Just about any of the IW uniforms are worth picking up, especially for Thor, WS, CA, BW, IM, Spidey, WM, SW, Thanos, Ebony, Corvus, SL, DS.
If you want to pick up some premium cards through legendary battle, consider the Ragnarok uniforms for Thor, Loki and Hela. Hulk’s Ragna uni is also great.
Other unis worth considering: QS, Venom (Anti-Venom), Shuri, ShaRog, Medusa, Emma Frost, Magneto, Cable.
There’s more decent options but I’d recommend going with the heroes you enjoy most from those possibilities.