It doesn't necessarily matter that there are quadrillions of possible openings. Studying traps that occur often in the openings you play is definitely helpful.

For example, if you're an 1. e4 e5 player you'll want to learn how to counter the Fried Liver attack, as it's one of the most popular lines at the beginner to intermediate level.

You don't need to know many lines 7 moves deep either, just a couple of moves is already very helpful.