Ability skilling:
You start off with two points in Heliogenesis, because this gives you max dmg output for the jungle gank and also max damage for jungling (yes you're a jungler). After reaching lvl 3, all points go to Core Collapse so you reach the overdrive as fast as possible (the overdrive halfs the CD and increases stun duration). Solar Storm is being maxed whenever possible.

Item build:
You start off with Energy Battery because you're gonna spam that Heliogenesis in your first two levels, and it builds into Clockwork, which you will be building. The reason you're not getting any crystal power is because you're going to be somewhat of a support in your team, and celeste also has a lot of natural damage. Solar Storm still can take half of someones HP late game even without any crystal power. The Crucible x2 is needed in this build because Celeste is naturally very squishy, and this obviously helps out with that. When you've got x2 Clockwork, the CD of your Core Collapse will be around 5sec!! This is the best stun-per-sec in the game, considering it's also an AoE stun!!

Team comp:
With this build, celeste is a jungler. BUT she's not the support jungler who gets an Ironguard Contract. She will take the carry role in jungle even though she's not really a carry. The best team comps I've found so far are:
Ringo(wp), Glaive(tank), Celeste
Adagio(wp), Koshka(tank), Celeste
Petal(wp), Catherine(tank), Celeste
Ringo(wp), Adagio(tank), Celeste

Try these out and you'll figure out why they work. My favorite of these comps is the one with Adagio and Koshka, because all of their spells synergize so well.

I stream a lot of Vainglory on twitch, so pop in and say hello when I'm streaming!
My stream link: www.twitch.tv/jetpackss

Cheers!