Hello guys my name is KinG#2784 and I play Heroes of the Storm since Alpha and my fav hero is November "Nova" Terra, the Terran Dominion Ghost. This build is made to instakill any squishi heroes in the game.
I will now tell you why I prefer to take this talents.
Ambush Snipe : As you know Nova is play'd in stealh mode all the time so this is the best skill you could get at lvl 1 so it can maxemize you're dps for all the game duration.
Gathering Power : Any skilled Nova will take "Gathering Power" as his 2nd talent, it gives you increaded ability power per kill. If you just started to play Nova you could take in consideration takeing Envenom
as it gives 750+ dmg at lvl 20.
Explosive Round : This the skill I prefere becouse it increase you're aoe dps by little but in a teamfight this is a must to have skill , many players asked me why I don't take Anti-Armor Shells but this skill makes youre attack speed so slow till it makes it useless.
Triple Tap : I prefer this skill over Precision Strike becouse it's a very good kill secure skill and it's damage is way bigger.
Advanced Cloacking : IT'S A MUST HAVE SKILL , Nova dosen't have self healing abilities so this skill gives you GREAT SUSTAIN in the whole game.
Crippling Shot : I prefer this skill becouse like the Guide Title says it's a must have to instakill combo work. When I engage somebody I use Pinning Shot then insta shot the Ambush Snipe , carefull you must do this combo in 1 second to work becouse when you are useing Pinning Shot you have only 0.8 second to shot youre sniper so it will work becouse the 20% dmg increase from Ambush Snipe works only when you shot it when you are under cloack or withing 1 second so be carefull.
Fast Reload : Well guys to tell you the truth this is my favorite talent. Once you get this the game will become much funnyer when you will just kill evryone and they won't know what happened.

Thank you for checking my Guide I will try to update it evry time something will change or some skill will get buffed. Good Luck and happy slayering.