Learn some really basic all-around meals you can build on. Woks, basic sauces, risottos, suff like that. You only need to have some basic ingredients like onions, canned tomatoes and spices around, then you just go with whatever you feel like eating or have lying around. You've got some leftover vegetables? Cook some pasta, fry a couple of onions and then throw everything in to the pan, fry a little and spice as you like. Not a world class culinary experience but beats the hell out of microwave meals and it's really easy and fast.

Cooking full proper meals isn't that time consuming either. It might take some time before you learn how to spice things to your liking and the first few times are pretty slow if it's all new to you, but it's actually quite fun and healthiness/taste/price is in a completely different league. You can easily find recipes online for whatever you like or just type in some ingredient that sound nice or you happen to have and see what comes up. Then just double everything in the recipe and even though it takes an hour or two and you screw up the first five times you try, you have just fed yourself for a week. In a few months you'll be cooking stuff that tastes way better than anything you can buy ready-made, for half the price and with little effort.

If you have no idea where to start try googling something your mom/dad/grandma used to make or something like lasagne, ground meat sauce, tuna sauce etc. My favourite effort to taste ratio is lentil soup, it takes a while to cook but you only have to cut the onions, put it all in a pot, let it cook and spice it.