So, looking to get into lc. Can anybody describe the meta to me? In terms of effectiveness and archetypes and stuff.
So here are some of the most meta defining mons when building (in my opinion, other people would point out different stuff probably).
Pawniard: This is a large part of the reason that fighting types (and Mienfoo in particular) are everywhere. Because Knock Off is so good in LC, since it instantly reduces Eviolite users defenses by a third for the rest of the match, Pawniard has a very spammable move. It's also very threatening after a defiant boost, works well as a fairy check, and is all around an effective, threatening mon. The most common set is Eviolite, although Scarf and LO are not unheard of.
Fletchling: You pretty much MUST have a counter or a whole lot of checks to fletchling when you build. Fortunately that's not too hard, since basically all electric, steel, and rock types will do. However Fletchling is fairly commonly paired with Diglett, so you have to be careful about throwing your counter out if they're grounded. Fletchling has basically one set, an itemless acrobatics one, but occasionally runs coverage like HP Grass or Overheat (although those aren't too common).
Mienfoo (and all fighting types really): Mienfoo is everywhere. It gets around 40/50% usage because it's so damn effective at what it does. It's decently fast, hitting the 17 speed tier, fairly strong, and has fantastic pivoting with regenerator u-turn. On almost all Mienfoo three slots are spoken for - a fighting STAB (either Drain Punch or HJK), Knock Off, Pivoting (generally U-turn, although Baton Pass is sometimes used), and a completely free slot that can be one of like ten moves (second STAB, SD, Stone Edge, Fake Out, Poison Jab, Acrobatics, Taunt). However Mienfoo's item choice and EVs aren't consistent. Eviolite is common, but in Eviolite there's a 0 Atk investment 17 Speed faster version, a slower version that runs much more bulk and provides a semi-slow pivot, and even some attack invested ones. Scarf is also fairly common, LO isn't unheard of although it's lost a lot of popularity, and there are even some custom sets like BandFoo. A different fighter you have to be aware of is Timburr, who has an effective Bulk Up set and unlike Mienfoo can actually take status thanks to Guts.
Setup Sweepers (Shell Smashers, Zigzagoon): Shell Smash sweepers are not rare, and you should probably try to have an answer to them in either the form of massive offensive pressure or something that can take the +2 attacks coming at your team, or by using encore from Cottonee the turn after they smash. Omanyte, Tirtouga, and Shellder are all threats that you should prepare for, as well as Zigzagoon who after a Belly Drum can tear apart most teams that are weakened slightly. One of the general catch-alls to these is Abra, who is a threat in its own right, since it can take any one attack due to Focus Sash and then KO back. Don't try using Abra on Shellder though, use a steel type.
Trappers (Diglett and Gothita): Yes they can be annoying during the match, and you constantly have to be playing around them. Diglett actually traps a lot of stuff you wouldn't expect, since it's fairly strong with LO and outspeeds basically all of the unboosted meta. It forms a lot of cores, and doesn't give up too much momentum after getting a kill. Gothita, on the other hand, can trap fighters and other mons using a scarf set and KO them. It also then loses almost all momentum, so take full advantage of it.
In terms of effective archetypes, full blown stall that tries to last 100 turns doesn't work too well in ORAS. People have tried, but generally it's just better to go semi-stall if you want to try that. Balanced and offense are both pretty good, and HO has been done successfully before. Sun and Sand teams exist, Sun has a pretty much optimized team by Mad0ka if you want to check that out (it's in the RMT archive), and can be difficult to deal with sometimes. Full Baton Pass teams are very matchup based but you might see one from time to time, it's important to recognize it in team preview. There are no Baton Pass clauses in LC by the way.
I didn't cover everything, but there's a lot of good resources on this subforum that you can and should check out if you're interested in getting into LC. Fortunately the teambuilder now EVs for LC which is nice. And welcome to LC!