I'm new to competitive battling, and this is my first team I've ever made. I had help with this team on a different website, but I joined here to get some more help.
The team I made is a Sunny Day team.
EDIT: I changed Ambipom to Jumpluff, and Houndoom to Arcanine.
JUMPLUFF (Used to be Ambipom)
Jumpluff @ Heat Rock
Jolly
Chlorophyll
108 Atk/252 Spe/150 HP
~Sleep Powder
~Sunny Day
~Encore
~U-turn
My lead is Jumpluff. Jumpluff, being one of the fastest pokemon in UU, is a great lead for my team. It can quickly put the opponent's lead to sleep using sleep powder. This will prevent my opponent from setting up, while at the same time allowing me to set up Sunny Day while they switch out their lead. After setting up Sunny Day, Jumpluff gets a massive speed boost. This will give me the advantage against my opponent, and allow me to U-turn out. If I need to set up Sunny Day again, I can send Jumpluff back in and use Encore. This will force another switch, and give me another free turn to set up Sunny Day.
I gave 252 speed EVs to Jumpluff to make sure it outspeeds other pokemon while the sun isn't up. It has 108 attack EVs to make U-turn cause as much damage as possible. 150 EVs are given to Jumpluff's HP to help it stay alive as long as possible
Tangrowth @ Life Orb
Jolly
Chlorophyll
252 Atk/252 Spe/4 Def
~Swords Dance
~Power Whip
~Earthquake
~Rock Slide
Tangrowth is my main Grass type sweeper. I chose to go physical over special with Tangrowth because Tangrowth gets Swords Dance to raise its attack. This attack boost along with the speed boost from Sunny Day makes Tangrowth a monster. One of the biggest threats to this team, Lanturn, doesn't stand a chance against Tangrowth. In the sun, Tangrowth will be able to outspeed most Fire types and use Earthquake to make quick work of them. Rock Slide is for flying types, specifically Moltres who is immune to Earthquake. These moves give Tangrowth great coverage, and make him a very useful member of the team.
252 EVs go to attack to make his moves hit as hard as they can. 252 EVs go to speed to ensure that he out speeds as many pokemon as possible who have around the same speed as Tangrowth with his boost.
Arcanine @ Heat Rock
Adamant
Flash Fire
120 HP/238 Spe/152 Atk
~Flare Blitz
~Extremespeed
~Morning Sun
~Sunny Day
Arcanine is my Fire type sweeper. I chose Arcanine over Houndoom because Houndoom needed a turn to use Nasty Plot, but Arcanine can attack right away. Flash Fire is used to switch in on Fire attacks. I chose Physical on Arcanine instead of special because of his higher attack, and Flare Blitz plus Extremespeed work great together. Flare Blitz, along with the boost from Sunny Day, does a lot of damage. Extremespeed is there to quickly finish off a pokemon while taking no recoil. Morning sun is important on Arcanine because of the recoil damage from Flare Blitz. Morning sun is even more useful on this team because of the extra health it restores. Since it is best to have as many pokemon as possible know Sunny Day, This set is perfect for it.
120 HP EVs are given to Arcanine to help with the recoil damage of Flare Blitz. 238 EVs go to speed so he can outspend other pokemon around Arcanine's base speed. 152 EVs go to attack for more powerful attacks.
Adamant
Sturdy
52 HP/252 Atk/204 Def
~Rapid Spin
~Earthquake
~Assurance
~Stealth Rock
When my opponent sets up entry hazards, I send in Donphan to Rapid Spin them away, and set up my own entry hazard. When my opponent sends in a fire type against one of my pokemon, I send in Donphan who resists fire, and can use a STAB Earthquake to take out their pokemon. Assurance is for when my opponent sends in a Psychic or Ghost type pokemon. With Stealth Rock set up, Assurance will do double the damage against their switch ins. Stealth Rock is the entry hazard that would benefit me the most, as flying and fire type pokemon who threaten my team, are weak to it.
I invested 252 EVs in attack because Donphan's way of attacking is using physical moves, so attack EVs would make Donphan hit much harder. 204 EVs go into defense to give Donphan more protection from physical attacks, and Donphan's special defense in too low to invest EVs in. 52 EVs go to HP to help Donphan sustain more damage without fainting.
The team I made is a Sunny Day team.
EDIT: I changed Ambipom to Jumpluff, and Houndoom to Arcanine.
JUMPLUFF (Used to be Ambipom)

Jolly
Chlorophyll
108 Atk/252 Spe/150 HP
~Sleep Powder
~Sunny Day
~Encore
~U-turn
My lead is Jumpluff. Jumpluff, being one of the fastest pokemon in UU, is a great lead for my team. It can quickly put the opponent's lead to sleep using sleep powder. This will prevent my opponent from setting up, while at the same time allowing me to set up Sunny Day while they switch out their lead. After setting up Sunny Day, Jumpluff gets a massive speed boost. This will give me the advantage against my opponent, and allow me to U-turn out. If I need to set up Sunny Day again, I can send Jumpluff back in and use Encore. This will force another switch, and give me another free turn to set up Sunny Day.
I gave 252 speed EVs to Jumpluff to make sure it outspeeds other pokemon while the sun isn't up. It has 108 attack EVs to make U-turn cause as much damage as possible. 150 EVs are given to Jumpluff's HP to help it stay alive as long as possible
TANGROWTH

Tangrowth @ Life Orb
Jolly
Chlorophyll
252 Atk/252 Spe/4 Def
~Swords Dance
~Power Whip
~Earthquake
~Rock Slide
Tangrowth is my main Grass type sweeper. I chose to go physical over special with Tangrowth because Tangrowth gets Swords Dance to raise its attack. This attack boost along with the speed boost from Sunny Day makes Tangrowth a monster. One of the biggest threats to this team, Lanturn, doesn't stand a chance against Tangrowth. In the sun, Tangrowth will be able to outspeed most Fire types and use Earthquake to make quick work of them. Rock Slide is for flying types, specifically Moltres who is immune to Earthquake. These moves give Tangrowth great coverage, and make him a very useful member of the team.
252 EVs go to attack to make his moves hit as hard as they can. 252 EVs go to speed to ensure that he out speeds as many pokemon as possible who have around the same speed as Tangrowth with his boost.
ARCANINE (Used to be Houndoom)

Adamant
Flash Fire
120 HP/238 Spe/152 Atk
~Flare Blitz
~Extremespeed
~Morning Sun
~Sunny Day
Arcanine is my Fire type sweeper. I chose Arcanine over Houndoom because Houndoom needed a turn to use Nasty Plot, but Arcanine can attack right away. Flash Fire is used to switch in on Fire attacks. I chose Physical on Arcanine instead of special because of his higher attack, and Flare Blitz plus Extremespeed work great together. Flare Blitz, along with the boost from Sunny Day, does a lot of damage. Extremespeed is there to quickly finish off a pokemon while taking no recoil. Morning sun is important on Arcanine because of the recoil damage from Flare Blitz. Morning sun is even more useful on this team because of the extra health it restores. Since it is best to have as many pokemon as possible know Sunny Day, This set is perfect for it.
120 HP EVs are given to Arcanine to help with the recoil damage of Flare Blitz. 238 EVs go to speed so he can outspend other pokemon around Arcanine's base speed. 152 EVs go to attack for more powerful attacks.
VICTREEBEL
Victreebel @ Life Orb
Modest
Chlorophyll
252 SpA/180 Spe/76 HP
~Weather Ball
~Solar Beam
~Hidden Power Ice
~Sleep Powder
Victreebel is my Grass type special sweeper. When in the sun, Victreebel becomes my fastest sweeper. I chose Special over Physical because Tangrowth is Physical, and having a special Grass sweeper would benefit my team. The first thing Victreebel will do is to use sleep powder if the opposing pokemon is a threat and if my none of my opponent's pokemon are already asleep. Solar Beam is there to hit Physical walls that prevent Tangrowth from doing much damage to. Weather Ball provides a powerful fire attack to use against other Grass or Poison types. Hidden Power Ice is used to combat Altaria, who is a threat to this team, and other flying types.
252 EVs are used for special attack because Victreebel is used as a special attacker, and would benefit from SpA EVs. 180 EVs are invested into speed to give Victreebel more speed, which also greatly benefits him. The remaining 76 EVs are used for HP to help Victreebel take some more damage.
UXIE
Uxie @ Heat Rock
Bold
Levitate
252 HP/252 Def/4 HP
~Sunny Day
~U-turn
~Yawn
~Thunderbolt
When I need to put Sunny Day back up, but my opponent has a water pokemon out, I can send in Uxie for support. U-turn lets Uxie escape after setting up another Sunny Day. Yawn is used to force my opponent to switch out if their pokemon is a threat to my team. If a water pokemon is out, Uxie can use Thunderbolt to take care of it. Since Uxie can take a hit, it can be sent in multiple times to set up Sunny Day or force another switch, which can ruin my opponent's attempt to sweep.
252 EVs go to HP to help with its low base HP compared to its defenses. 252 Defense EVs are used to help Uxie take physical Dark attacks.
DONPHAN
Donphan @ Leftovers
Victreebel @ Life Orb
Modest
Chlorophyll
252 SpA/180 Spe/76 HP
~Weather Ball
~Solar Beam
~Hidden Power Ice
~Sleep Powder
Victreebel is my Grass type special sweeper. When in the sun, Victreebel becomes my fastest sweeper. I chose Special over Physical because Tangrowth is Physical, and having a special Grass sweeper would benefit my team. The first thing Victreebel will do is to use sleep powder if the opposing pokemon is a threat and if my none of my opponent's pokemon are already asleep. Solar Beam is there to hit Physical walls that prevent Tangrowth from doing much damage to. Weather Ball provides a powerful fire attack to use against other Grass or Poison types. Hidden Power Ice is used to combat Altaria, who is a threat to this team, and other flying types.
252 EVs are used for special attack because Victreebel is used as a special attacker, and would benefit from SpA EVs. 180 EVs are invested into speed to give Victreebel more speed, which also greatly benefits him. The remaining 76 EVs are used for HP to help Victreebel take some more damage.
UXIE

Uxie @ Heat Rock
Bold
Levitate
252 HP/252 Def/4 HP
~Sunny Day
~U-turn
~Yawn
~Thunderbolt
When I need to put Sunny Day back up, but my opponent has a water pokemon out, I can send in Uxie for support. U-turn lets Uxie escape after setting up another Sunny Day. Yawn is used to force my opponent to switch out if their pokemon is a threat to my team. If a water pokemon is out, Uxie can use Thunderbolt to take care of it. Since Uxie can take a hit, it can be sent in multiple times to set up Sunny Day or force another switch, which can ruin my opponent's attempt to sweep.
252 EVs go to HP to help with its low base HP compared to its defenses. 252 Defense EVs are used to help Uxie take physical Dark attacks.
DONPHAN

Adamant
Sturdy
52 HP/252 Atk/204 Def
~Rapid Spin
~Earthquake
~Assurance
~Stealth Rock
When my opponent sets up entry hazards, I send in Donphan to Rapid Spin them away, and set up my own entry hazard. When my opponent sends in a fire type against one of my pokemon, I send in Donphan who resists fire, and can use a STAB Earthquake to take out their pokemon. Assurance is for when my opponent sends in a Psychic or Ghost type pokemon. With Stealth Rock set up, Assurance will do double the damage against their switch ins. Stealth Rock is the entry hazard that would benefit me the most, as flying and fire type pokemon who threaten my team, are weak to it.
I invested 252 EVs in attack because Donphan's way of attacking is using physical moves, so attack EVs would make Donphan hit much harder. 204 EVs go into defense to give Donphan more protection from physical attacks, and Donphan's special defense in too low to invest EVs in. 52 EVs go to HP to help Donphan sustain more damage without fainting.