Buffed champions: Iron Man Luke Cage Mr Sinister Gladiator Superior Iron Man
7* are not the future but present, and you got Titania. Prioritize her rank ups. Several good options from your 6*, Juggernaut, Doom, Cosmic Ghost Rider, Tech Spiderman, Chavez, Iceman, Ironman, Sunspot, Hercules, Spiderham, Kingpin, Torch, Sinister, Hyperion, etc. It's more like a personal preference or need depending on what content you want to do next.