Highly recommended coloured contact juggling ball. It's one of the cheapest Acrylic contact juggling Ball with good enough quality. You may buy clear balls for main balls and buy colored ones for accents. It'll be good looking if you make isolation moves with colored balls.
You need to buy acrylic ball to start multi ball contact juggling, otherwise it never start. If you want to start multi contact juggling, I recommend you to buy 4 ( at least 2 ) you can play with 2 balls on each hand. If you have them in your hand during watching movie in your home, you'll get smooth after the movie, that's the way I practice :)

*Don't leave them in the Sun, Acrylic Ball can burn or even make fire in your home.