I presume you want to bulk?
If you want to keep costs down, there are some cheap and good forms of protein out there, its not all that bad
Eggs, Cottage Cheese/quark, chicken breasts, tinned tuna etc
Bread, rice, oatcakes, quinoa etc arent that expensive either
I know what you mean though... but If I am being honest and you are short of cash, supplements probably arent worth your time yet