Gaara and Rock Lee are both pretty important, so that's good. ;) You may also want to keep an eye out for Rock Lee's teammate Neji (who has long black hair and white eyes), and Gaara's teammates Temari (the girl with four blonde pigtails) and Kankurou (in a black catsuit and face paint.)

The others will get a good introduction as soon as you need to know who they are. Though honestly, you don't really need to keep the three Sound ninjas straight.