i have been on a similar diet most of the time. you’re gonna have to focus your budget on protein sources, then get cheap fats and carbs.
make your own Big whey gainer shakes. I actually realised with the Whey i was buying (a quality isolate) each serving was cheaper than most whole food protein sources.
Whey+oats+olive oil+fruit+milk+whole eggs or whatever else twice a day, big cals
Coconut oil- lots of saturated fat calories, cheap
Cheap cuts of beef an meat in general
cheap beef burgers (check the nutritonal value though. some can be pretty good)
Fast food burgers- cut out the fries and sugary soda (or get diet), this can work well. especially post workout
sandwiches- a couple slices of bread and a can of tuna with some hot sauce or mustard, cheap and easy
Tomato sauce- add chilli powder or hot sauce to tomato paste/puree, chop up some onions and peppers, pour it over whatever meat you’re frying up for flavour, even works with tuna and eggs
stir fry cheap veggies with meat
shop at fruit and veg markets, butchers, fishmonger markets ect
if youre gonna get supps, dont be fooled into anything other than whey, maybe fish oil, cheap pure creatine, just basics.
its not going to be a ‘lean mass diet’, but you will gain just fine, make up for your lack of quality nutrition by going even harder in the weight room.