Have you read the beginners’ guide? I highly recommend reading many of the guides that are pinned here.
Aside from that, the generic advice I’d offer is patience. This game is intentionally designed to be a grind. This way you never get ahead of netmarble. They always keep you wanting more. I’m a year in & I’m still not at the highest level (cards/CTPs/T3s). And I’ve followed all the guides & spent plenty of money.
You’re at the first wall, of many, that this game throws at you. It will take significant time, both daily & overall. So, you have to ask yourself how committed you are. If you do want to continue to play, & invest said time into the game, then you’ll have to be tactical. Early on, you don’t have enough resources to achieve multiple goals without spending ridiculous amounts of money. So, focus on 2 characters at a time. One farmable, and one world boss. Start with Quicksilver, after you finish Wolverine & Deadpool.
I would advise you to stop leveling DS & Loki to 70. Getting Thor to T3 is fine if you have the ccf. Cap would be better, but at this point you may wanna finish Thor.
Focus on attaining more T2s, getting the game-changing uniforms, & improving your cards. Per cards: all attack, skill cooldown (25+), ignore defense (30+), & max hp. You’ll have more energy attacker’s than physical, but all attack is preferable.
Shuri, Sharon Rogers, Winter Soldier (needs IW uni) are essential. But again, you need depth. Your primary focus should be shadowland. Make that your goal. It requires depth. Read some guides. Track your progress.
Also, anytime that you’ve completed all your dailies, and done all your farming (this includes X-men), you should do all 3 WBI. This is a great way to get materials at a good rate. Use all your energy before bed and let it refill overnight. Do your recharging of energy before reset everyday. You’ll have to learn a cycle of play based on your availability. It is very time consuming to get the most out of the game, but it’s that or spending significantly.
Hopefully this gives you some direction. If you need more, DM me or message in 336 English. People are here to help. Try and have fun!
It is ok, you are still on the early part of the game.
If I were you I wouldn't worry about Thanos WB just yet, it is not worth the effort and you are better off farming mats from the other world bosses.
Right now you should focus on getting more T2 characters and their uniforms if you can afford them. Basically every IW uniform is worth it. For example, Winter Soldier goes from a trash tier character to a A+/S character.
Don't worry about the Giant Boss Raid mode right now, you need well built characters to do it.
I see some of your ISO-8 sets besides Loki and Thor are not offensive. Try to get as many offensive ISO-8 sets as you can and equipo your characters with obelisks that suits them. i.e. Your Dr. Strange would be better off with a GBI/Crit Dmg/Proc.
Try to get a roster that helps you clear as many Shadowland floors as you can, since this is a good way to get some bio selectors for non farmable characters through story mode, such as Iron Hammer.
I hope this helps a little.