So you mention you like veg in sauces, how are you with Mushrooms and spinach? I have a decent recipe for a pasta that my veg averse teen really loves.
I chop up a pack of mushrooms really small, throw em in a pan with some olive oil and pepper, loads of garlic (dried or frozen, or even lazy garlic will do)
Pour in a tub of cream, lower the heat, stir frequently, add in some dried mixed herbs, and grate in cheese.
Obviously throw your favourite pasta on,
A few mins before your pasta is finished, add spinach.
It's my daughters favourite but because of the high calorie content I don't cook it too often!
Bananas are a great start! Things will improve over time, it just takes time!
If you like omelette but haven't ever cooked one, I make my omelettes in a cake tin, with baking paper to stop them sticking! I've never been a lover of eggs so when I tried to introduce omelettes into my diet, I just made it simple for myself!
Pasta bakes can definitely be a cheap meal that puts weight on! If you're looking for cheap, quick and easy, I used to love cacio e Pepe. (Or my bastardised version of it!)
All you need is olive oil, butter, salt, pepper, cheese, and spaghetti.
Pop the spaghetti on,
Heat olive oil, loads of black pepper, small pinch of salt, and about a tbsp of butter about 7 minutes after spaghetti gone in.
Grate yourself quite a bit of cheese,
Keep a mug of the pasta water aside,
Spaghetti in the buttery mixture,
Then throw in the cheese, toss it around a bit, add a splash of the spaghetti water, when it's sort of smooth and silky serve.
Ah. I miss that meal. Nice with proper Italian cheese, but because I couldn't bare spending the money I started using normal mature cheddar, or on occasion parmesan.