I'm pretty decent with bmx bikes! Bmx Bikes correct? If your gonna buy a bike online & gear. I Would recommend this site called Dan's Comp. My brother built a bike there, and i used to buy gear there, and now i increased to a 850$ Custom BMX bike. But if you wanna pick one upp quickly, and have someone to talk to about the bike your looking at. Go to a local bmx store. But yes about the diamond back. That brand is pretty good!
If it's mountain bikes i have no clue at all, and if it's bmx bikes. i hope i helped xD!!