what kind of food can you feed or prepare for your cat apart from the store bought/packaged ones?

Chicken, beef, fish. Keep it a carnivorous diet or your cat will get sick. You can feed cats and dogs raw meat, they usually prefer it that way. Some people are uncomfortable with that, you can cook it too.
If you really want to get into it you can look up nutrition guidelines, they’ll help you out.

Any meat, cooked and cooled mixed with a small amount of vegetables like spinach, carrots and peas but only tiny pieces, sometimes sticking it in the blender is good, easier for the cat to digest the veges and sometimes if they're too big and obvious they act like kids and eat around them so hiding them is good

Fresh meat! Pork is a favourite.