There’s a book called “Poverty Prepping” that might help. And you can borrow foraging books from the library. If you find some nice wild edibles that are going to seed, grab some and scatter them where you like.
Game meats are all over most cities, but you may need a trapping license. Here in WI, those are cheap, and people might pay you to get rid of their racoons for them.
Just a couple thoughts while my sleepy meds are kicking in.
Aside from the library, download Amazon.com’s free Kindle to your PC and scroll through their $0.00 prep and life skills books.
As others have said, cut back on or cut out eating out and all the other frivolous wants. Stick to needs. Cut out all the little trips to the grocery as those add up and you end up wasting money on junk. Try to cut down grocery trips to once or twice a month with just the bare basics. That saved gas $ goes into the food budget. Every gallon of gas used would have been 6-7 cans of 50c veggies. Instead of buying one food sale item, buy as many as your budget allows.
Keep your eye out for yard sales and thrift stores. I wouldn’t make a special trip for those but if you’re passing one, stop in. On the flip side, you probably have a ton of preps at home if you just thought about it. Do a good house cleaning and decluttering but think about how items could be used in prepping before discarding them. Have a yard sale with what you really can’t use and put the proceeds into your prep budget.