Hey, congrats on doing your own work. I usually just take my Giant to the shop I picked it up at, but occasionally I'll do some adjustments myself.
Do they offer a kit? Kits for bikes are usually quite simple, so it keeps the cost down from buying tools individually and you don't get swamped with a kit that is half full of unnecessary tools. The go-to brand for most shops seems to be Park Tool, but I'm sure other brands would be fine. Pick up a cheaper basic set, then get your own cable and housing cutters and you should be good to go. A basic kit should include all the essentials like a chain whip, cassette socket, bb tool and pedal wrench. Most other tools are not really bike specific, and unless you're doing major overhauls you should be fine with something simple.