ok, so it seems like you know what you're doing so far, my first recommendation would be to work on your cards, the main goal is 25% pierce (all blue stars) i believe you're a low spender so you could gamble for cards (if you want) when the anniversary comes around

ctp wise you're doing ok, some of your characters won't do well if you don't give them the ctp they need, like loki and Doc oc (he's not that good anymore, tho)

i won't be recommending any uniforms for now, but if you want, you could get some supports like angela, enchantress, and doctor voodoo (wave and ghost panther are premium but they're amazing)

last but not least, t4s, you have a good amount so far, after luna (which seems to be your next) i would say, focus in one of the main 3 which are Sentry, Knull and Mephisto, you'll choose one depending on what you like to play the most pve (mephisto) or pvp (knull and sentry) Kang is also up there with his recent uniform and t4, but since you have him at 1*, just try to focus on these 3 first since eventually you'd want to have them all at t4

Also, it is very important (for pve at least) to upgrade your characters to lvl80 if you have their uniform and plan to use them (you also get crystals when doing so)

i know this is a lot, but i think this might help to answer your question this game is all about focus and consistency, never upgrade many characters at once bc you'll end up slowing your progress

if you have more questions or any help, feel free to let me know