Its all about the fun. Take your time and find out what kind mountain biker you want to grow up to be. Techno junkie(roots,rocks,logs), down hill bomber, xc, freestyle… Many options and each has its own setup/gear.
I used to live in Suwanee and rode here couple times a week.
http://www.singletracks.com/bike-trails … woods.html
Never got up to Roswell trials you mentioned but I have friends that say they are great. Lots of stuff up in the North Georgia Mountains as well. You’re in a good area.