Need advice

R2D2 is arguably the best overall character you can have in this game: https://swgoh.gg/meta-report/#all

And is useful in just about every situation that he is allowed to participate in. Get him for sure.

I pulled up your roster, but didn't really look too close... You don't have some of the legendary toons (R2, Thrawn...) So for sure be working on Phoenix, Rebels, and Empire. Just pick 5 of each faction and keep building them up and don't spread yourself too thin and try to work on 15-20 characters at once.

That should keep you busy for a while, but also consider getting in front of the curve, too. As in R1 and First Order.

Yeah I realise I was pretty vague. I don't like seeing the same teams in arena too often so I like to mix things up a bit whilst trying to remain a little competitive.
So I've switched to a rex lead, fives, zylo, anakin, and now old Ben. I find this team fun on offence but realise it's not perfect at holding its rank, partly due to only having 2 G11s as of right now. I want to try and keep up with everyone but gearing up is slow so I don't know whether to concentrate on these or switch up.

Acquiring legendary characters is one of the things that's confused me, I'm trying to prepare for when the events circle round, especially the R2 event. But juggling these events as well as thinking about arena and said teams is a bit overwhelming!

I'll try and prioritise getting him then, thanks for your help!

Get rid of Fives.

And get thinking about synergy between characters.