The general rule of thumb is: if you're ranking to qualify for a progression title, rank the champs you use the most. There's no perfect champ to rank up for progression purposes. Its going to be the ones that you will use the most to do the content in front of you. I would probably be leaning towards focusing on Domino, Serpent, and maybe Crossbones, but there's other good options in there.By the way, if you're going to ask for rank up advice, it would be helpful to state, or use filters to make obvious, which champs are at which ranks. Without knowing your masteries, this is not going to be obvious to most players from just looking at PI.