do you have cupboards with spices, stock cubes, flour, passata etc? pots and pans and things like that too? and do you have a budget?
I only ask cause it is going to be much more expensive to begin with if you are having to buy e.g. a bottle of soy sauce for a recipe so it wont be cheaper at all to start cooking from scratch but will be longer term.
I generally think having a well-stocked cupboard is the key to being able to cook well
super easy vegetarian things:
quiche: buy some shortcrust pastry pre-rolled. sometimes you get it reduced to clear and it is suitable for freezing. millions of recipes for all sorts of different recipes online. I’m making one on Sunday with courgette, pine nuts and frozen peas. pine nuts are quite expensive so you can leave them out.
with most basic curry recipes you can replace the meat with chickpeas. if you are short of ingredients, I find fresh ginger is the best thing for giving it loads of flavour and spiciness. also chopping up some cashews will be a good protein substitute but again this might be too expensive.
one of my favourite super easy quick meals is: grated courgette lightly fried with olive oil, garlic, the juice of a lemon, pine nuts, a teaspoon of capers. served with linguini +seasoning.
in terms of Mexican things, my favourite is enchiladas and tbh these are better than the ones in that restaurant last week.
French onion soup is very cheap to make and can be so delicious. good way to use reduced to clear bread.
these things are handy: https://www.tesco.com/groceries/en-GB/products/256538133
tbh I really suggest reduced to clear sections in supermarkets (you probably know this obviously). for my dinner tonight I had a 9p cheese sandwich that I made into a toastie and added some vegetables and flavours.