Then use oil and applies this advice. Since a few years, I have had to out butter in my regular diet but olive or vegetable oil replace it very well in any place but toast and pastry.

You can put spice, condiment and premade sauce on every thing. You can cook many thing with spice or condiment around it (rubed on or mixed in cooking water), the result will be different than added at the end.

Patatoes
Eggs
Cheese
Rice
Legumes (lentils, beans, chickpeas…)
Salt
Oil
Vinaigre
Spices

This make a cheap but healthy diet that can be cooked as something terribly bland in texture and flavor or extremely flavorful and diverse in texture depending on what you like.

Add bread sometimes and you can makes hundreds of recipes.

You have a small budget but since eggs and cheese are pricier in many places, by reducing them, you can easily add the legumes and oil.
Sometimes don’t buy potaoes and replace it with rice.
Do use salt, it is crucial for health and for making a recipe work.

This way, you bugdet should stay the same.

Now, for spices, there is two routes :

1 - Buy prepackage mixes. They are cheap for the unit, the easiest to squize in a budget that can’t be streched any further. After a few servings the package is used up, so you can change the flavor for the next time. But they have additives that make them not the healthiest. But if you don’t eat or drink anything but water and what you say this is more than healthy compare to most people

2 - build you spice (and herbs) cabinet. Spices outside of blends are cheaper but sold in bigger format so you need more money in the short run. You might find the money by reducing slightly further cheese or eggs once a groceries trip every month or every six weeks and buy one more jar of spice to use in your cooking. If you are cooking for yourself and since you are not used to cook with spice yet, take a small size not the biggest one even if it is cheaper by the ounce. Focuse on what is used the most in your cuisine : For a westerner culture, it would probably start with pepper, then garlic powder, then oignon powder, then a herb mix, then paprika. You can get inspiration for ingredients in you favorite premade mixes to know what to buy next.

Choose an oil that has a neutral taste and that can be heated a lot (sunflower or canola) so it could be use in plenty of way. Use it generously, it help with feeling full, better tasting food and weight retaining.

Legumes can be bought in tins. They are very cheap, already cooked perfecty, for a price premium already flavored. They can be eaten cold, as a salad with a bit of acid from the vinaigre.
At the beginning eat small portions or you get flatulences. With the time, your body will get use to digest them.
Legumes can be smash/blend in sauces, soups or spread. They can be place on the side of potatoes or rice.

When you are use to them (you know which one you like, which ones you eat the most), buy them dry. It is even cheaper and makes your groceries bags much lighter. It is not complicated to cook but it you have to figure out how to manage a budget, eat differently and gain weight, make it easy on you and start with the tins.

White vinaigre is so cheap. You buy one bottle and it least very long. It is much more acid than lemon juice so it is used in very small quantity. But it is not flavorful, just acid.

For specific recipes, it will depend on :

• your time available
• the cooking equipment you have
• the space you have

But I speak from experience, with a very very small space and limited cooking equipment these ingredient can bring you very far.

Other useful cheap ingredient you might buy from time to time are :
All-purpose flour, baking soda, semolina, oat, granulated sugar. They will add even more diversity and will make you a pantry from which many dessert can be cooked.
Tins vegetable are cheap…ish. They store well, so they can be bought in advance when you got a little room in your budget or when there is a nice reduction. Same with the cheapest kins of jams and preserved fruits. Some frozen vegetable are cheap as well but you need a freezer, freezer space and to use electricity to store them.

I currently need to learn how to cook for people with diet very limited in diversity. I’m on a budget and want to do it healthy. So I would be very interested to know how your diet evolved and if I can be of any help don’t hesitate to message me. I’ll help you to the best of my advices.

Cheers