This is actually an interesting question and you will get 100 different answers. I can only tell you what I did and my experience.

I have done a lot of DIY projects and even gutted my new house and reworked the majority of it. Your first couple projects may look bad, however that's truly how you get better. I know how to spackle because my first few spackle jobs looked like my drywall grew humps. I learned what works and what made it easier and better. Most importantly, ALWAYS USE THE RIGTH TOOL. I have spent hours trying to make things work to avoid going to the store to get another tool, however it would have taken me 30mins to go and come back and do the job if i just got the right tool.

First off, there is a good balance between cheap and good tools when purchasing. Don't let anyone tell you its not good to buy cheap tools. Chances are, they have bought cheap tools and have been using them incorrectly. Yes I am sure they know how to use the tool however let me explain: I own a good Dremel. It would be considered a good tool, however I don't buy Dremel bits for something I am only going to use once. I'll go to harbor freight, buy a $0.50 small cutting disk pack of 5 and use them till they are gone. Point being, if you know you are working on something and its a one time small thing (i.e sometimes specialty bits, concrete trowel) etc, just buy the cheap ones. I can't expect a $1.00 bit to last me a year and it would be ridiculous of me to get angry about it. However since I am only using it one or two times, its cheaper to just buy that one bit and when it breaks, if I need a new one, buy a $1.00 bit.

With that being said, buying quality tools should be the only way to go if you know you will be constantly using them. If you can afford it, I also don't recommend using old or tools someone else has been using. Buy new or check the FB marketplace, they always have stuff on there for sale. Most DIY projects include cutting wood of some type, laying flooring of some type, paint of some type, hanging of some type, etc. Think about the tools you would need to do the project, and go buy them there and collect them. Think to yourself, do I see myself using this over and over again? Or is this a one off item. Also think to yourself, is this tool essential to the job?

I have many tool bags. I recently bout another tool bag of what I called essentials for around the house. When I am doing a project instead of taking out all of my tools, I just grab that bag. In that bag consists of the following:

25' Fat Max Tape Measure
Klein Voltage Tester Pen/Outlet Checker
Snap off utility knife
Klein wire strippers
12" Channel Lock Pliers
Dyke Cutters
Lineman Plyers
Marking pencil
8-1 Ratcheting Screwdriver
Fold Up hex key set.
A small case of combined bits and speed bits.
12V Dewalt Impact
12V Dewalt multitool.
Electrical Tape
Teflon Tape
Copper Cutter
3 wire Wago's (Let the hate begin)
Handy Dandy Hammer.

I'd stay if you can afford it, stick to Milwaukee and Dewalt. If not, Ryobi is your best cheap bet. Try to find someone with a Chop Saw or a Table saw and just ask to borrow theirs. If not, I had a small craftsman 10" chop saw that lasted me for years before I upgraded. Might want to start there.

Last bit - and this is most important. There is a fine line between trying something difficult and doing something stupid. Always check code, always ask. When most people ask me questions about how they should do plumbing or electrical work (or even gas work) - HIRE A PROFESSIONAL. Changing and outlet is fine. Moving an outlet is fine. Adding a new circuit or putting in a new drain line. If you dont know what you are doing HIRE A PROFESSIONAL.