Since others have given you much of the base advice, I’ll just throw a few extra random points in.
a. Everybody makes the mistake of opening a LT too early and getting a 5*. If you worry too much about what this might be doing to your scaling, then sell it. That said, with the move to SCL for PVE, the only place where there’s an impact is PVP, and the impact is overrated if you only have 1 5*. Don’t get a second one until you’re ready for it, which is when you have a good collection of 3* champs.
b. Play DDQ. Every day. Go as far as you can, and don’t be afraid to use your 5* BSSM; his hit points and match damage won’t help. I didn’t see a 1* on your roster; if you don’t have one, get a good one (and only one); like Iron Man or Juggs. You can clear the first DDQ node with only one, and that’s 500 points, a token and helps get the bigger tokens every day. You should always clear the first three nodes, and you can probably clear the 4th one (Dat Required Character) most days.
c. Find a PVE SCL level that works for you. Given your roster, this is likely to be SCL 4, but that’s OK; the progression rewards will really help.
d. Don’t worry about PVP. Certainly play it if you’d like, but don’t worry about your results. Consider it a good success if you get to 300; the rewards are still worth it.
You’re doing fine. You already have 6 2* champs; you don’t need more to progress, although like the others have said, you can’t have too many 2* champs. Don’t farm anybody you need to win matches until you don’t need them any more (probably OBW, Ares, Wolverine, Thor, Torch, and I would champ Hawkeye, Storm and Mags ASAP; my 2 go-to teams in 2* land are OBW/Wolvie/Torch and Storm/Mags/Thor; others have other teams, but the point is you can’t go wrong with them). Once you don’t need them any more to win matches, then you can start selling and rebuilding them (which is what farming is), but only when they get to level 144. For now, your teams are going to be mostly 2* with some of your better covered/leveled 3* to help out as needed. Soon, you’ll start getting more 3* and that’s the point you start to transition.
MPQ is a “slow and steady” kind of advancement model. Sure, you can dump a whole lot of $$$ and advance quickly, but unlike many FTP games, you don’t NEED to spend money to advance. I kick a few dollars to the devs every month since they deserve to get paid, but honestly I get a lot more by just playing than I do by paying. And there are a lot of people out there with very advanced rosters who have never paid a cent.
I hope this helps; and good luck!