Note: You might try the Health & Fitness forum for more on this subject.
How old are you? If you are in your early/mid teens, you do not want to overdo the plyometrics. I have heard this from several expert sources on the subject. Skipping/jumping rope a lot is fine tho'. It is considered a low-level plyometric exercise that can provide superb benefits for tennis footwork and conditioning.
The primary reason that elite sprinters move so fast in a short time is that they have a high % of fast-twitch muscles in their legs. For the most part, it is something that you are born with. OTOH, marathon runners have a high % of slow-twitch (endurance) muscles. The best you can do it to work with what you've got. Plyometric exercises primarily works the fast-twitch muscle fibers.
Another way that sprinters get a very quick start is by being off-balance for their first few steps -- the are actually "falling" for their initial steps. You can do the same with your tennis footwork. Drop steps, gravity steps, and mogul moves are some of these off-balance footwork patterns.
Another way to get your self a bit off-balance for a quicker start is to modify your split-step timing slightly. If you land your split-step as your opponent makes contact, you will need to land on the balls of both feet. However, if you are just a split-second later with your split-step, you are more likely to land on one foot. This can possibly result in a slightly quicker start. Make certain, however, that you do not execute the split-step too late -- it can cost you precious time getting too the ball.
Every tool is a weapon -- if you hold it right. (~Ani DiFranco)