Normaly when I start on Gotham Heights as Batman, I go straight for the Atomic Axe (1). I play it safe, at the same time helping my teammates capture points, farm to gain coins so you can get your next items.
The beginning of the game is always the hardest part, you want to stay alive as long as you can to gain coins from farming and capturing, as well killing enemy teams. If you find yourself getting poked a lot by enemy team, back off, go to your nearest health/will pad and come back to help out your team mates, if needed go back to base. If you are in a sticky situation, make sure to utilize your stolen powers.
Know when to engage fights for example 3v1, 1v1, team fights, etc. Know when to fight under enemy turret (if needed).

Cant see the score properly, but K/D/A is 9-2-5 and this wasn\'t full build.
I hope this guide is useful to you.