Embrace this truth: CONVENIENCE PRODUCTS AREN'T REALLY ALL THAT MORE CONVENIENT. Look at just about everything in your pantry, fridge, bathroom vanity, cupboards, and laundry room and realize that you can make your own version of pretty much anything in there, probably cheaper and with much less effort than you'd ever guess.
Instant oatmeal? Making your own takes 3 minutes instead of 90 seconds and tastes ten times better. Birthday cake and frosting? Google "one bowl chocolate cake" and "easy buttercream icing" and spend maybe an extra 5 minutes total, and you've got something inexpensive and much healthier (and you can sneak some whole wheat flour into that cake too, if you feel like it!). Slap some tomato sauce, leftover veggies and meat, and mozzarella cheese onto a piece of naan or pita and you've got personal pizzas that are way better than pre-made frozen ones. Canned veggies, like tomatoes and beans? Learn to can your own tomatoes and cook and freeze amazingly cheap dried beans in your slow cooker, and you can nix those. And speaking of the crockpot--you can make yogurt in it, a big batch, which you can then flavor with all kinds of things and put into reusable containers for school lunches. Those boxed "whatever-helper" meals or frozen dinners? Make friends with your crockpot: some veggies and possibly meat dumped in there with a jar of salsa or spaghetti sauce or whatever, in the morning, means a delicious ready-made dinner that night. Deodorant? Google that, and you'll find recipes from the simple to the complex that work just as well and don't involve rubbing aluminum onto newly shaved armpits with their proximity to breasts and lymph nodes. And lots of folks here have mentioned vinegar with essential oils (and if you don't have those, just drop the peels of some lemons and oranges into a mason jar of vinegar for a couple of weeks, and you've got essentially the same product) diluted in water as an amazing cleaning liquid.
Make friends with Google Search, not to mention the other ladies on this page and all over the Internet. You don't have to do it all, of course; just try things one at a time, and add as you feel ready. You'll be amazed what you can do, with very little time and money. And repeat after me: ANYTHING THEY CAN MAKE, I CAN MAKE CHEAPER.