Hey!

I ask someone last week (i think) about a pushing build on Nova and tried it to a certain extend (5 or 6 games to this day, not extensively). I'm very enthusiastic about it because i had the same reservation than you about Nova and really didn't like playing her knowing that if i was shut down by good positioning or a very tanky comp i would be utterly useless. I think this build is very viable on Mine even though i would much rather play an other hero but sometimes you get stuck with the map in QM.

Build:

LvL 1: Psi-Op (allows for longer snipe and cdr is good)

LvL 4: Perfect Shot (I tried Gathering Power and Perfect Shot, my preference lies with Perfect Shot at the moment, lets you harass without worrying about mana and you don't give up that much damage), also if you manage your mana well enough you just never go back to base.

LvL 7: Explosive Round (Snipe on the caster minion will kill it and deal around 50% damage to the whole wave if you cast it properly with the right timing)

LvL 10: As you prefer but i always liked Precision Strike better. I don't think one is better than the other though.

LvL 13: I don't know yet. I used to pick Lethal Decoy (clone deals 25% of your damage) for those long range kill on a fleeing enemy but i might like Headshot better now. Advanced Cloaking might also be considered but it doesn't matter much which one you pick for this build to work.

LvL16: Railgun (That's the must pick, with it you'll clear a wave in approximately 3 second. When a wave is coming, snipe all the minions for a 1 sec cd snipe, snipe it again and you are done, you have no cd on any skill, it's very good).

LvL 20: Whatever you need, i almost always pick Bolt of the Storm, it's too good to pass up on Nova imo.

Try it!