How about something substantial for dinner? Knorr Rice sides are cheap as hell and super easy to make. repack them in a freezer bag, add 1.5ish cups of boiling water, let sit for 5-10mins $1 for a hot meal with good amount of calories. you're not a small dude i'm sure you will want to eat more than snacks.
Instant mashed potatos are also damn cheap and super tasty if you get something like garlic flavor or something. again repack in freezer bag, follow the directions for water. $1-1.50 1 packet is pretty big and weighs very little.
i usually do
breakfast:
oatmeal/cream of wheat, cup of hot chocolate
snacks/lunch:
trail mix, pop tarts, granola bars, pb crackers, pringles (140cal per ounce)
dinner:
knorr side or potatos, candy bar