I'm a college student so for the time being I don't have a lot of money to spend. That said, I think I do pretty well for myself considering I can only spend about ~$30-40 per week. I usually eat 3000-4000 cals daily.
I've found that frozen veggies are the way to go. Canned veggies don't taste good and lose their nutrients. I usually keep 1-2 lb. bags of collards, turnip greens, spinach, and broccoli in the freezer.
Also, I've forced myself to like frozen seafood because you can get it at very good prices. Typically I get all my seafood for $4/lb or less. I find good deals on octopus, squid, whiting, shrimp, clams, salmon, etc.
Nuts are always expensive but sometimes if you buy in bulk (1 lb or more) they are a little cheaper. I mostly almonds and walnuts but if I have extra money I'll go for buy pecans or macadamias for a treat.
I get most of my carb intake from fruits. The ones I've found with the highest carb to dollar ratio are raisins, bananas, oranges, apples, peaches, and pears.
I really wish I had money for grassfed beef, but I just settle for the least processed and leanest meat I can find. Sometimes I get the omega-3 enriched eggs but usually I just eat 20-30 regular eggs per week.