EDIT** I'm not new at all to competetive, but I havn't been on these forums for long, os if its in the wrong section my apologies.
OK, i'm not going to exaggerate by saying
"OMGZ IS IS AWESOMZ HE IS LIEK THE NEW GARCHOMP EVERYONE SHUD USE HIM HES COOLER THAN THE BALL AND CUP GAME"
However, I will prove his effectiveness in battle.
Firstly, his base stats. Fair at best, yeah. BUT what makes Ariados so good then? The answer? His MOOVEPOOL
- Toxic Spikes
- Baton Pass
- Agility/Spider Web
- Sucker Punch
- Shadow Sneak - priority moves are good since his lack of speed
- Night Shade - helps against those irritable types
- Bug Bite - Plucks away those yashe and lum berrys
- Pursuit
These are some of his awesome moves. But it can't be just his movepool, eh?
Insomnia. Personally one of my favorite traits, as he blocks out Hypnosis, and especially screws up the plans of those Sporing Smeargles/Brelooms. (A lot of people are looking for ways to counter Breloom, he also resists grass and fighting 0.25, and since a lot of Breloom dont carry stone edge this is good) If you don't have a restalker on your team then the insomnia trait can be invaluble.
Also, Ariados is a nice poison type. Meaning he brushes away those toxic spikes. Thanks to his insomnia trait too, he can absorb Sleep and poison, making him a great member to have. Also, poison types can use black sludge, which will mess up those TrickZams, Jirachis, Bronzongs etc..
Here is a good set that i'm using atm. It doesn't fully abuse his movepool but it works great (also, Ariados is one of the best breloom counters in the entire game)
Ariados (F) @ Black Sludge
Impish Nature (+Def, -SAtk)
Trait: Insomnia
EVs: 212 HP / 84 Atk / 212 Def
- Night Shade
- Poison Jab
- Sucker Punch
- Toxic Spikes
Actions speak louder than words, so read this battle log:
(Hotel Yorba is my Mamoswine, Ariados comes in after a bit)
Begin Turn #1
Miltank used Body Slam!
(146 damage)
---------------------------------
Hotel Yorba used Stealth Rock!
Pointed stones float in the air around PP-P2's team!
---------------------------------
End of turn #1
PP-P2's Miltank: 353 HP
Kryuell's Hotel Yorba: 216 HP
Begin Turn #2
Miltank used Body Slam!
(138 damage)
---------------------------------
Hotel Yorba used Endeavor!
(275 damage)
---------------------------------
Using Salac Berry, the Speed of Miltank rose!
End of turn #2
PP-P2's Miltank: 78 HP
Kryuell's Hotel Yorba: 78 HP
Begin Turn #3
Hotel Yorba used Ice Shard!
(78 damage)
Miltank fainted!
---------------------------------
PP-P2 sent out Weavile (Lv.100 Weavile)!
Pointed stones dug into Weavile!
End of turn #3
PP-P2's Weavile: 213 HP
Kryuell's Hotel Yorba: 78 HP
Begin Turn #4
Weavile used Ice Shard!
(78 damage)
Hotel Yorba fainted!
---------------------------------
Kryuell sent out Arachni (Lv.100 Ariados)!
End of turn #4
PP-P2's Weavile: 213 HP
Kryuell's Arachni: 334 HP
Begin Turn #5
Weavile used Ice Shard!
(98 damage)
---------------------------------
Arachni used Toxic Spikes!
Poison spikes were scattered all around PP-P2's team's feet!
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #5
PP-P2's Weavile: 213 HP
Kryuell's Arachni: 256 HP
Begin Turn #6
PP-P2 withdrew Weavile!
PP-P2 sent out Houndoom (Lv.100 Houndoom)!
Houndoom was poisoned by Toxic Spikes!
Pointed stones dug into Houndoom!
---------------------------------
Arachni used Poison Jab!
(177 damage)
---------------------------------
Houndoom is hurt by poison!
Arachni restored a little HP using its Black Sludge!
End of turn #6
PP-P2's Houndoom: 6 HP (Psn)
Kryuell's Arachni: 276 HP
Begin Turn #7
Arachni used Sucker Punch!
(6 damage)
It's not very effective...
Houndoom fainted!
---------------------------------
PP-P2 sent out Dragonite (Lv.100 Dragonite)!
Pointed stones dug into Dragonite!
Arachni restored a little HP using its Black Sludge!
End of turn #7
PP-P2's Dragonite: 250 HP
Kryuell's Arachni: 296 HP
Begin Turn #8
Dragonite used Dragon Dance!
Dragonite's Attack rose!
Dragonite's Speed rose!
---------------------------------
Arachni used Poison Jab!
(92 damage)
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #8
PP-P2's Dragonite: 158 HP
Kryuell's Arachni: 316 HP
Begin Turn #9
Dragonite used Fire Punch!
(257 damage)
It's super effective!
---------------------------------
Arachni used Poison Jab!
(95 damage)
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #9
PP-P2's Dragonite: 63 HP
Kryuell's Arachni: 79 HP
Begin Turn #10
Arachni used Sucker Punch!
But it failed!
---------------------------------
Dragonite used Dragon Dance!
Dragonite's Attack rose!
Dragonite's Speed rose!
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #10
PP-P2's Dragonite: 63 HP
Kryuell's Arachni: 99 HP
Begin Turn #11
Arachni used Sucker Punch!
(63 damage)
Dragonite fainted!
---------------------------------
PP-P2 sent out Magnezone (Lv.100 Magnezone)!
Pointed stones dug into Magnezone!
Arachni restored a little HP using its Black Sludge!
End of turn #11
PP-P2's Magnezone: 279 HP
Kryuell's Arachni: 119 HP
Begin Turn #12
Magnezone used Substitute!
Magnezone made a Substitute!
---------------------------------
Arachni used Night Shade!
The Substitute took damage for Magnezone!
Magnezone's Substitute faded!
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #12
PP-P2's Magnezone: 205 HP
Kryuell's Arachni: 139 HP
Not the most epic, but I managed to set up TS, aswell as killing Dragonite and Houndoom (even with type disadvantages)
I hope this post helps your competetive battling! Ariados does extremely well in UU, and can even hold his own against OU.
OK, i'm not going to exaggerate by saying
"OMGZ IS IS AWESOMZ HE IS LIEK THE NEW GARCHOMP EVERYONE SHUD USE HIM HES COOLER THAN THE BALL AND CUP GAME"

However, I will prove his effectiveness in battle.
Firstly, his base stats. Fair at best, yeah. BUT what makes Ariados so good then? The answer? His MOOVEPOOL
- Toxic Spikes
- Baton Pass
- Agility/Spider Web
- Sucker Punch
- Shadow Sneak - priority moves are good since his lack of speed
- Night Shade - helps against those irritable types
- Bug Bite - Plucks away those yashe and lum berrys
- Pursuit
These are some of his awesome moves. But it can't be just his movepool, eh?
Insomnia. Personally one of my favorite traits, as he blocks out Hypnosis, and especially screws up the plans of those Sporing Smeargles/Brelooms. (A lot of people are looking for ways to counter Breloom, he also resists grass and fighting 0.25, and since a lot of Breloom dont carry stone edge this is good) If you don't have a restalker on your team then the insomnia trait can be invaluble.
Also, Ariados is a nice poison type. Meaning he brushes away those toxic spikes. Thanks to his insomnia trait too, he can absorb Sleep and poison, making him a great member to have. Also, poison types can use black sludge, which will mess up those TrickZams, Jirachis, Bronzongs etc..
Here is a good set that i'm using atm. It doesn't fully abuse his movepool but it works great (also, Ariados is one of the best breloom counters in the entire game)
Ariados (F) @ Black Sludge
Impish Nature (+Def, -SAtk)
Trait: Insomnia
EVs: 212 HP / 84 Atk / 212 Def
- Night Shade
- Poison Jab
- Sucker Punch
- Toxic Spikes
Actions speak louder than words, so read this battle log:
(Hotel Yorba is my Mamoswine, Ariados comes in after a bit)
Begin Turn #1
Miltank used Body Slam!
(146 damage)
---------------------------------
Hotel Yorba used Stealth Rock!
Pointed stones float in the air around PP-P2's team!
---------------------------------
End of turn #1
PP-P2's Miltank: 353 HP
Kryuell's Hotel Yorba: 216 HP
Begin Turn #2
Miltank used Body Slam!
(138 damage)
---------------------------------
Hotel Yorba used Endeavor!
(275 damage)
---------------------------------
Using Salac Berry, the Speed of Miltank rose!
End of turn #2
PP-P2's Miltank: 78 HP
Kryuell's Hotel Yorba: 78 HP
Begin Turn #3
Hotel Yorba used Ice Shard!
(78 damage)
Miltank fainted!
---------------------------------
PP-P2 sent out Weavile (Lv.100 Weavile)!
Pointed stones dug into Weavile!
End of turn #3
PP-P2's Weavile: 213 HP
Kryuell's Hotel Yorba: 78 HP
Begin Turn #4
Weavile used Ice Shard!
(78 damage)
Hotel Yorba fainted!
---------------------------------
Kryuell sent out Arachni (Lv.100 Ariados)!
End of turn #4
PP-P2's Weavile: 213 HP
Kryuell's Arachni: 334 HP
Begin Turn #5
Weavile used Ice Shard!
(98 damage)
---------------------------------
Arachni used Toxic Spikes!
Poison spikes were scattered all around PP-P2's team's feet!
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #5
PP-P2's Weavile: 213 HP
Kryuell's Arachni: 256 HP
Begin Turn #6
PP-P2 withdrew Weavile!
PP-P2 sent out Houndoom (Lv.100 Houndoom)!
Houndoom was poisoned by Toxic Spikes!
Pointed stones dug into Houndoom!
---------------------------------
Arachni used Poison Jab!
(177 damage)
---------------------------------
Houndoom is hurt by poison!
Arachni restored a little HP using its Black Sludge!
End of turn #6
PP-P2's Houndoom: 6 HP (Psn)
Kryuell's Arachni: 276 HP
Begin Turn #7
Arachni used Sucker Punch!
(6 damage)
It's not very effective...
Houndoom fainted!
---------------------------------
PP-P2 sent out Dragonite (Lv.100 Dragonite)!
Pointed stones dug into Dragonite!
Arachni restored a little HP using its Black Sludge!
End of turn #7
PP-P2's Dragonite: 250 HP
Kryuell's Arachni: 296 HP
Begin Turn #8
Dragonite used Dragon Dance!
Dragonite's Attack rose!
Dragonite's Speed rose!
---------------------------------
Arachni used Poison Jab!
(92 damage)
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #8
PP-P2's Dragonite: 158 HP
Kryuell's Arachni: 316 HP
Begin Turn #9
Dragonite used Fire Punch!
(257 damage)
It's super effective!
---------------------------------
Arachni used Poison Jab!
(95 damage)
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #9
PP-P2's Dragonite: 63 HP
Kryuell's Arachni: 79 HP
Begin Turn #10
Arachni used Sucker Punch!
But it failed!
---------------------------------
Dragonite used Dragon Dance!
Dragonite's Attack rose!
Dragonite's Speed rose!
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #10
PP-P2's Dragonite: 63 HP
Kryuell's Arachni: 99 HP
Begin Turn #11
Arachni used Sucker Punch!
(63 damage)
Dragonite fainted!
---------------------------------
PP-P2 sent out Magnezone (Lv.100 Magnezone)!
Pointed stones dug into Magnezone!
Arachni restored a little HP using its Black Sludge!
End of turn #11
PP-P2's Magnezone: 279 HP
Kryuell's Arachni: 119 HP
Begin Turn #12
Magnezone used Substitute!
Magnezone made a Substitute!
---------------------------------
Arachni used Night Shade!
The Substitute took damage for Magnezone!
Magnezone's Substitute faded!
---------------------------------
Arachni restored a little HP using its Black Sludge!
End of turn #12
PP-P2's Magnezone: 205 HP
Kryuell's Arachni: 139 HP
Not the most epic, but I managed to set up TS, aswell as killing Dragonite and Houndoom (even with type disadvantages)
I hope this post helps your competetive battling! Ariados does extremely well in UU, and can even hold his own against OU.