This achievement will unlock pretty early on if you continue to play the game normally. I wouldn't worry too much about it honestly. The best way to leveling up in this game is completing quests.
So kill zombies, complete main/side quests & work on other achievements and you should get this before finishing up Act 1.
If you really want to get this, just farm alcohol or something for one of the continuous quests and complete those over and over. Although I wouldn't recommend this unless you have duplicated/infinite items.