This is a spend money to save money in the long term tip, but if you have the space for it (garage, basement...), an energy efficient chest freezer is a solid investment. Whether you're feeding a lot of people, just a few, or just yourself. It will allow you to take full advantage of big sales and load up on a lot of perishables that would otherwise go bad before you can use them. If you go through a lot of beef, you can now buy a half or quarter of a cow from a local farm, generally for much cheaper. If you garden, it makes it easier to preserve a lot of produce, whether things that don't can/dry/pickle well or things you haven't grown enough of to justify all of the effort of canning/dehydrating. And it opens up a lot more options for saving leftovers/prepping/batching, so it can be a time and effort saver as well. If you cook a big batch of something, realistically you're likely to get sick of it before you're through it, and might end up throwing a lot of it out. If you can freeze it in portions, you'll have a much better time and waste less. Do this with a number of meals, and now you have a variety of easy premade choices on days when you're sick or too wiped to want to cook anything from scratch and are tempted to go waste money on fast food/delivery/takeout/eating out.
A lot of older recipes are also budget recipes and are centered around how to minimize waste (think WWII ration-era cooking, Great Depression-era cooking, and so on). Many modern recipes call for a ton of ingredients, not uncommonly specialty things you won't use up in the dish you're making with them and won't use often, so they'll either expire or sit in a cupboard collecting dust indefinitely. Ingredients you buy but don't use up waste money. Focus on recipes with a short, simple list of ingredients and meal plan in ways that dovetail to use up any extra perishables you might have Meat is expensive, but the meatloaf principle holds: you can pad out ground meat substantially with bread crumbs, vegetables, and/or grains to make it stretch further in a satisfying way. Think mixing shredded zucchini into ground chicken patties or sausage, making goetta, 'emergency steak' (as seen on Tasting History), or again, meatloaf.
Aside from when it's miserably hot or freezing, don't just turn your thermostat up/down, turn it off. For most of spring and fall, you might not need it at all. Adjust and adapt to the little bit of discomfort this might cause, and strategically open and close windows to help regulate in warm weather (cross breezes and cool night/morning air are both useful resources, try to capture them). The times I've done this, it knocked my energy bill down to around $40 a month.
In the short term, this sounds glib, but the biggest thing is to keep your spending under control and live within your means. Track every purchase and payment, sit down with your receipts, and give yourself an audit. Identify and trim the fat. Make a budget and stick to it. Cancel any little subscriptions you don't need or use that seem small enough to not bother with but add up to a big drain.
If you have a tendency to impulse spend (grab a candy bar or whatever else wasn't on the list at the grocery store, buy random things online), it's time to curb it. It's an expensive way to farm dopamine and an easy way to get yourself in a financial hole. Set a budget, make lists that fit within the budget, and stick to the list exactly. If you struggle with this, you can even gamify it a bit while you develop financial discipline with two lists: a list of positive and negative things and rewards/penalties assigned to them (think 'every week under budget' = $1 plus whatever you saved, 'every unplanned purchase' = -$5, if you've got any habits you're trying to develop or shed, can multitask and add these in), and a wishlist of things you might normally just buy but don't need. Instead of buying those things when the urge strikes, put them on your wishlist. Then just 'earn' money towards those wants by following the goals laid out in that first list. Odds are when you've earned enough reward money to afford them, you won't want some of them anymore. Congrats, you've just saved the money you would have wasted on it.
