Finally got 3 tech t4cc. What to do?

Snurris

I finally have the chance to get a 4* up to rank 5 (Stark spider or Star-Lord, both awakened) or a 5* up to rank 3 (Ultron, unawakened)
But I can’t decide. Pls help.
Thank you!

Solswerd

Considering you are at the stage of the game where this would be your first rank 5 4*....Starlord won't do that much for you.
Both Stark Spidey and Ultron are solid choices. I would look at synergies, and also take into account which champ you enjoy using more. Ultron's poison/bleed immunity along with his regen can be very useful. Stark Spidey has his own bag of tricks that can be a big help as well.