Light Lance shows promise as a viability, and I plan to experiment with it later, but at the moment Black Hole just comboes so much better. Black Hole + Heliosphere is NUTS in a teamfight, and it sets people up to be stunned/damaged by your Void Step (If you skilled into that, more on that later) Black hole is definately superior until proved differneltly, as while Light Lance may be able to take out 4/10ths of a single opponents's health if they stand still while the slow-moving projectile trundles towards them, later on a well-placed Black Hole can take out 1/3 of every enemy's health, with little to no time to react. Black Hole is evidently superior.

I advise 3 points into Black Hole and 2 into Powerups for Celestial

For Void Step, I've taken 3 in damage since if I get close to a group of enemies I can Black Hole-Heliosphere-Void Step to do massive damage. Take 2 in stun, as it also does a good AoE debilitation to enemies. Movement Speed seems sorta good as a chase/escape helper, but Helios is all about AoE combo and it doesn't really help.

For Heliosphere, it's really personal preference. I've taken 3 into Timing and 2 into duration, but any combination is really viable. Duration-Area is good for scaring enemies off while you're trying to capture the chest, Area-Timing could be viable as combo, as Area makes sure that Timing will do it's full extra damage.

Do not check that little tempting "Reccomended Build" icon. It goes for Light Lance, and it is overall terrible for any character, since builds, especially Void ones, should be dynamic.

Start out by getting a Void item, otherwise your ult will be Light Lance. I usually get Void Shroud (Head-Hoods) and then upgrade it to Executioner's Hood as soon as I can. For your next item, get Ragged Belt. Then take a look at the enemy's lineup. Do they have stuns? Hangman's Noose. Silence? Nullifying Belt. If they have little to no of either or they have Hamhock, take Nothing Left to Lose. Then get your Void Walkers. Move on to Starshard, and then Vitriol Cloak.

Gameplay style:
You're an AoE nuker/disabler thriving in teamfights or chase. Imperative: DO NOT VOIDWALK INTO ENEMIES UNLESS YOU HAVE STUN+DAMAGE AND/OR ARE CHASING! while chasing, Voidwalk and then immediately Black Hole.
YOUR COMBO:
Black Hole-Heliosphere directly on the center of the Black Hole. The delay works so that if cast consecutively, the Heliosphere will just pop up as soon as enemies are sucked into the middle.

Little tidbits:
If an enemy's trying to get a big buff or the chest, make it hell for them. Cast Heliosphere right next to them, so it chases them and interrupts. Cast Black Hole on them for good AoE nuke and to interrupt. When they realize that they're too low and need to get out (Such as with a big buff) Voidwalk right into their faces and blow them up.

When capturing the chest and if enemies are thinking of interrupting, cast Heliosphere on the little bridge. They won't want to take the damage they'll be given if they run through it.

Did I miss something? Did I make a error? Want me to add something? PM me or comment! I'll be sure to reply soon.