I made my shelves out of wood because the steel ones were very expensive at first, R$800.00 per meter. Since my father was a carpenter, I asked him to make a wooden model, and it worked out well. I opened three convenience stores with wooden shelves, and it was a great success. My grocery store had some machinery that was essential at the beginning, such as a computer to record sales (because without it, you have no idea how well you're selling and which products are selling), a refrigerator, an island display case, and I also bought a butcher's cold storage unit to store beer for customers, which worked very well. You can also set up your own mini-market without money; you just need to have other cheaper options for everything you're going to do, or you can even do the work yourself, as that's how I started, making the vegetable stand and everything myself.
If you have Telegram, join the group here.
https://t.me/MeuMercadodoZero