I bought DCS A-10C in the recent Steam sale, as I've never played a flight sim before and thought this would be a good opportunity to find some time to get into one. However, I haven't loaded it up yet because I know that peripherals are pretty essential for a flight sim. Based on the various Giant Bomb podcasts and videos, I know that I probably need a HOTAS and possibly a TrackIR. Is this pretty much it, or would I need/want something else?

No, that's pretty much it. Make sure your HOTAS has a rudder twist or you'll need some pedals as well. TrackIR in really helpful, but I wouldn't call it a necessity. You may want to make sure sims are for you before taking the financial plunge into that.

Welcome to the club!

You can find some great used HOTAS sets online. I ended up getting a Saitek X45 pretty cheaply.