Good choice ... you'll be glad you have one. Hognose snakes have lots of behavior and personality, so they're easy to love no matter what color. If you don't want to spend a lot, I'd suggest hets from trusted sources otherwise find a normal that you like (such as the greens that you mentioned). Normal Hoggies are highly varied in appearance. If you don't want to spend $1000 ... or more on anerys, Toffees, and Anaconda morphs, get a high red or green normal.
As for humidity, like you mentioned, go with a small water dish. And for substrate, lots of people use aspen bedding, care fresh, or newspaper. Best of luck, they're a hardy and forgiving species for the most part. Adam