I don't think the dumbbell squats are a bad idea. Most basketball players make the mistake thinking that plyometrics alone will make them run faster and jump 30 inches higher. It's what all those programmes promise, they want to make it sound easy so that people buy them. Also doing squats will help your positioning on defence and post play.
The truth is that to gain speed and quickness you need a combination of training methods, including plyometrics, leg strengthening exercises like squats, a lot of sprinting (ideally in a competitive environment to push you to the limit), high protein intake, and a lot of rest between sessions.
if you want it more specific here are two articles on speed