I'm a new player, its my 16th day on the game and i already have two champs at lvl 60 full ascended(Kael and apothecary). 

 I have bought Kael's masteries but not apothecary ones yet.

I didnt have that good luck in my openings. I got a couple of usable epics and a legendary but they are far to be gamechangers.

What do i have? 

Errol or Relickeeper.

If i decide to bring to 60 any of the two would be exlusively to focus on my Arena offensive. Im ok with it, i like the arena.

Luthiea or Elhain

Any of her has potential in Arena but i think they can be used on dungeons too, dont they?

Luthiea could be potentially useful for clan boss but the A1 doesnt seem to be reliable... i cannot book her.

Rearguard sergeant

I think she is one of the best epics i got. Her ally protection is kind of decisive in some areas. But is it worth leveling her up to 60? Shes at 50 and works just fine.

Thanks in advance!

Other champs i have at 40/50 

Draconis(really helpful at my lvl of account)

Warmaiden(most used in Arena)

Jinglehunter(used only for his aura)