the cheapest and easy to find with lots of proteins is EGG
Then all the meat and fish are usually rich in proteins but considering that it is not healthy (nor good for the planet) you should not eat too much meat especially beef and pork
Fat fish like tuna are also rich in proteins. tilapia, sardines
All kind of dry beans, especially soja beans (and soy milk) and monggo beans, easy to find here!
Also peanuts and cashew nuts
Jackfruit (lanka) avocado and guava are also good source of proteins
Note: having an only protein diet is not good... always balanced dapat ang diet!