Juggling is an excellent way to deveop skills for soccer. The repetition of touching the ball to control and keep it within reach is a great way to develop touch and get a feel for manipulating the ball. Juggling, or touching the ball again and again and again, helps to develop a feel for the ball that will build confidence while increasing focus and dexterity. The various angles and body positions required to make the ball do what it is you want it to do translates nicely into game play. Juggling helps develope the ability to strike the ball properly and consistently and helps players develope eye/foot coordination which is essential for recieving and controling or striking a soccer ball.
It is not as simple as just learning how to juggle. In other words, it’s not how many times you can juggle a ball without it touching the ground, it’s what you do with those touches that count. The point of learning how to juggle is to make the ball do what you want it to do. Master the ball.
Using a smaller ball like the Brasilian Futebol or even a tennis ball can accelerate progress and sharpen eye-foot coordination as well as develop balance, agility, quick feet and touch. Becoming an accomplished juggler with a small ball will make it easier to control and manipulate a regulation game ball.
If you are just learning here is a good place to start: