you need two of the same card you fuse

Cards have three levels, a card level, an ability level, and a mastery level. mastery is gained randomly and from succeful attacks and defense, ability level will not matter much till later,  Little Empire Mojo but card level is really important, you get this by boosting your main card with weaker cards (example use spiderman to boost black widow) this takes up alot of cards and money but it is important to max level cards before fusing them to get higher stats out of them, this is why we dont care about boasting uncommon cards,  Little Empire Mojo there too weak to last long enough with the rare cards you got, so just use them as boast, if a card is at max level and you boast it, then your boasting ability,  Buy Little Empire Mojo you dont have to max ability or mastery before fusion, just the card level.

 

If you didnt get at a card better then rare out of you ultimate tickests then i recommend you start with black widow, if you can get another black widow fast, then keep her, if not then switch to the rare storm you get later on,  Cheap Little Empire Mojo because you get two of her fairly early (you need two of the same card you fuse) so you wind up with a nice fused S Rare card earlier then most players, after fusion storm will drop back down to level one so you still have to max her level again.