I suggest you try it out with the champs you feel best using. If you don't know which champs you should be bringing (or can bring into it) you might want to stick to classic.
Well dude first you'll have to be comfortable with doing Uncollected 100% then you'll need certain champs or classes to do them like I recommend Variant 3,2 in any order again depending on champs.Right now you have no powerful Tech champ for Variant 3 and no #XL champ for Variant 2 and you clearly don't have a diverse roster for Variant 1.So here's my advice to you just focus on Act 5 100%, uncollected & Master 100% and Arena as you build your roster. I know this isn't the answer you wanted.But TBH you only need Sentinel to do both Variant 3 and 2 since he's both a very powerful Tech and a #XL champ. Variant 1 I would only recommend the completion.
Hey, if you want to tackle variant start with either 2 or 3, since you don't have a lot tech champs go for variant 2, you can use gulk and dorm as they are XL champs and few champs that use heavy as a source of damage such (domino trinity and heavy spam, AA, Hype)
Do variant 2 , use domino-masacre-redhulk, only hit heavy, she will destroy it. I explored variant 2 with a rank 4 domino.
But TBH you only need Sentinel to do both Variant 3 and 2 since he's both a very powerful Tech and a #XL champ. Variant 1 I would only recommend the completion.