Rice (cook from scratch or use plain microwaveable ones for a quick meal) and potatoes, esp sweet potatoes, and wholegrain bread (lowest sugar you can find) for starchy carbs.
Eggs, tuna, canned beans for protein.
Veggies—leafy green stuff like spinach, broccoli, kale as a base, but as many different colours and types as you like.
Fruit—a piece or two a day is good for you.
Dried herbs and spices to add flavor and interest to meals—eg, I love having boiled eggs with a tiny bit of salt mixed with cumin. Adding some herbs to a salad or pre marinating meat with some olive oil, salt and pepper, and whatever spices you like, elevates it completely.
I’d also say bulk buy and meal prep for the week and it should save you money/ keep you on track. Rice, eggs, tuna, frozen veges, fruit are all great options and are quite cheap. I’d suggest chicken for your meat as it can be quite cheap