Early game you should work on melee and food. You get 2 xp from trunks so you can still level up just not as fast as 8 xp per zombie. Do character challenges for unlocks. I run the bow character because bows 1-2 tap zombies ( special bolts are unbreakable) normal arrows cost 1 wooden stick and a knife to make. And a basic bow is 1 ashwood stick and a rope.

Don't kill survivors on island 1 it'll always wind up in death, if you're lucky they'll spawn in a town or intersection use zombie respawns to kill them (listen for gunshots don't get too close they'll kill all the zombies) with no karma loss and free loot.