Who to rank up?

Clifford7

I don't currently have enough to rank up all of the champions shown but im wondering if and when I do have the resources who should I take up?

One would think it should be sparky but I'm currently struggling with balancing my champions between war and AQ map 3 and 5 but I also want to progress in Act 4. So I guess my question is should I widen my roster to balance out my different rosters by taking up iceman (or anyone else other than sparky) or just save up for sparky? Or anyone else that might not be obvious to me?

Molo

Of the ones available to rank up, Cyclops.

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colbyscipio987

Black Panther Civil War

JOHNOSA1995

Ice man hulk sl(need dup)

buddy20

stark

Thunder5715

Iceman, vision, sparky, rouge can't go wrong with any of those. Hulk and crossbones are also good options.
And it's always better to progress with 6-8 champions rather than going all in into one.