Water, Dark, Steel, Fairy, and Flying are all good types for laddering.
Rain Water lets you sit back and relax as you click, make the opponent explode, then double back to Toxapex/Gastrodon/Quaquaval in case the opponent seems to be threatening/un OHKO'able but will OHKO your swift Swimmer (Eg. Sucker punch Kingambit, Choice Scarf Meowscarada in case of Basculegion-F)
Balance water has access to one of the sturdiest cores in the meta rn, and teaches you how to play slowly, learning which mon checks what, and breaking holes/cleaning up the opposing team when time is right.
On the other hand, Dark is sort of the type you want to play when you wanna know how to setup a win offensively; Learning which mon thrives in what matchup and preserving and wallbreaking with them as much as possible makes Dark teams really fun to play. However, Dark is very much cteamed in the ladder (esp in early ladder where everyone is Bug) and has issues with entry hazard control, which is sort of well...a problem.
Steel is like balance water in a sense that it covers its weaknesses well due to having a pokemon immune to each of its weaknesses. However, its flawed in a sense of it having no true check to certain mons like Urshifu-R and Skeledirge. It has Corviknight and Gholdengo though, which are op guys.
Fairy is a little like Dark but trades the little defense Dark has (Sableye + TingLu ) for moar offense, some entry hazard control (magic bounce Hatterene) and dual screens. Its Hyperoffensive in a sense that almost everyone sets up and sweeps, so its good if you just wanna see damage go brr. However, Steel is pretty common rn, and Fairy has issues getting past certain pokemon, notably Corviknight.
Flying just has a variety of good mons, and immunity to spikes in an entry hazard metagame (everyone spams entry hazards, since removal is less than the actual setters). Its great anyway though, but has to pick matchups to win against, as threats like Greninja, Baxcalibur, Fluttermane, Chien Pao and Spectrier exists, and you cant cover all of them. Does well into ladder though...somehow.
I hope these help in making a decision on what to use. Sample teams will be updated soon, but you can check
that and the
bazaar if you need a team like right now