Ant troubles

My husband and I began renting a house back in February. Well, since its started getting warmer, we've been fighting ants. I've tried ant spray, and that kills them on contact, but doesn't stop them from coming in. I tried putting ant powder around the doors and outside window ledges to keep them from coming in. Nothing seems to work!

This morning I woke up, and grabbed the nag of cat food, we keep it on top of the fridge because that's the only place it seemed they wouldn't get to it, and ants were all over the top of the fridge and im the food bag, same with dog food.

Anything I can do that actually works??