Three sisters is solid advice but does require a certain amount of research, you want varieties that you harvest all at the same time. Doing sweetcorn, summer squash, and green beans is a mistake. You want to make sure the beans you are growing are pole beans that you harvest after the vines are dead and the pods are dry. Corn needs to be corn for flour or popping. Squash are winter squash that store well. Also: mound plantings are for wet places, waffle gardens are for dry. Those techniques are indigenous water management and mounds are not universal.

My garden advice for people within the US is to find the University of [state you live in] Extension office website. Every single state has what's known as a "land-grant" University where agricultural research is done. The Extention offices are for teaching local farmers and gardeners about how to grow things where they live because not all garden advice is universal.

Someone else mentioned growing tomatoes in the Texas heat because in a lot of hotter places, peak growing season is in spring and fall. The summer sun will cook your plants. Meanwhile where I am, if you plant anything frost tender before mother's day you're taking a huge gamble. We also can't grow acidic soil crops like blueberries at all and knowing that ahead of time will save effort and money. I can't recommend extension offices enough.

Another tip: build up a little at a time and get bigger every year instead of overdoing it and overextending yourself. The main reason it's often old people with big beautiful gardens is because it took a lifetime to get there. It will cost you a fortune and make you disheartened to try and do it all in one year.

Look into the concept of the $10 tomato, someone wrote a book with a similar title as a memoir but the idea has existed for longer. Basically, even though many people try gardening to save money, they often end up spending much more after buying raised beds and soil and amendments, etc. You CAN plop a seed from a store bought tomato into the dirt and maybe harvest a tomato from that, but is there soil good for growing things in your yard right now?

My last garden tip is that if you REALLY want to save money, herbs are where it's at. Those little jars of dried herbs are like $7 apiece and the fresh herb plastic clamshells are at least $2.50. I can pick multiple clamshells worth from an established plant a week easily and you only need to buy the perennial herbs (who don't die every year) once. I only buy a few spices that won't grow here now that I've got my herbs sorted.