Research a few food stores near where you live, and determine which is cheapest, and especially determine if one does certain things cheaper than another.

If your budget can stretch to it and you feel competent, cook with fresh veggies. Your will feel the difference in your energy levels.

Turn electrical stuff off when not using it.

Don't forgot to include "fun money" in your budget. Unless you're a monk, you'll spend it anyway, so may as well plan around it.