Die grinder is all you need for 99% of your cutting. The only things you might need to know about using one is, 1. Buy the biggest air compressor you can afford. Die grinders eat air like you won't believe. 2. Has already been mentioned - buy the best quality brand you can, etc. It doesn't cost any more to go first class. Do NOT buy such items from the likes of Harbor Freight. (Have I touched a nerve here?)
Yep, I bought a plasma cutter. A good one at that. After rewiring my garage for 220 (in spite of what it says, 110 won't push it.), adding a dryer (they don't like moisture in the air.) and up-grading my air compressor (same rules apply as die grinder, they eat air.), I am in so deep that I cannot possibly sell. If you lived next door, you could borrow it. Wait, I don't lend tools so that won't work. (My neighbor borrowed my Mantis tiller to do a small job. That was 3 weeks ago. Darn, I hate to lend stuff. Neither a lender nor a borrower be.)