Okay, here are my two cents:
containers: pretty much everything can be used as container.
For sowing or sprouts you can use yogurt pots and also some of the boxing … bowls from the supermarket (please remember that I’m not a native speaker). Or you can make little sowing pots out of old newspaper (not sure about toxins in the printing colours) or packaging paper.
For plants requiring little space, such as old oven dishes or cake tins, old tetrapaks, mugs, pots and pans, old cans (from olive oil or tomatoes …) also a lot of vegetable packaging (from the supermarket) can be filled with earth, you just have to make sure there are holes in the bottom to allow excess water to drain. If there aren’t a courageous use of a drill may solve this problem.
Bigger plants such as tomatoes and co. can be planted directly in the bags your flowers soil comes in. Also big empty food cans from the central market are great if your have access to one.
If your are buying fertilizers and soil: Don’t fall for advertisement lies such as “you need different soil for different plants” - True there are some plants for which this is true such as ericaceous plants, orchids and citrus plants but mostly this is propaganda. Just buy soil for universal use and fertilizer for vegetables (it’s a bit better than universal fertilizer but it’s not important if it’s fertilizer for tomatoes or fertilizer for strawberrys). It’s important to have both, but which kind, that’s just details.
I have no experience with homemade compost and fertilizers, but there are a lot of fascinating ways of making them from kitchen scraps and suchlike which are suitable for small spaces, so it may be interesting to look into that…
As for tools: be creative! A sturdy bough or chopstick often is as effective as a dibber (is this a thing?) or some professional tools. A sharp knife should be found in every kitchen (be careful!) and some pruning shears are extremely useful but not essential.
It’s a great adventure learning about plant breeding and growing your own seeds! If you want to harvest your own seeds you’ll need to invest at least one time in quality seeds for your basis which you then can breed. Be careful to buy seeds which are NOT hybrid seeds (I don’t know how the opposite kind is called in English. In German we say ‘samenfest’). You need to buy seeds which are true to itself so you can again and again harvest seeds for the next growing season. Also I think it’s cheaper to sow your own seedlings vs. buying them in the garden center. Ont the other hand buying grafted plants (tomatoes, cucumber, eggplant) may yield a bigger harvest…
Wow, this turned out to be quite a wall of text. Hopefully there is something useful in there… Please excuse my poor English, if some things are not clear enough feel free to ask.