Bouncing 3 balls is easy and kinda boring (for me). you can bounce practically anything with three and it doesn’t really matter. you can get some super cheap super balls or something just to mess around with, then decide you like it enough to get expensive balls later.
If you want to do “real” bounce juggling, like 5 balls, I would suggest learning to throw 5 first if you don’t already, then bouncing 5 will come easier.
I had some rubber bouncy balls and was going to learn to bounce 5, but that was before I could throw 5 very well and I lost some of the balls first.
I can bounce 5 continuously off a wall though…
Well, when I end with three in one hand I quickly move the first two around with my fingers to make room for the third… I’m sure you already do that though.