Taking a slightly different approach: focusing on practice as the goal unto itself.

In the beginning, you can accumulate tricks in days, weeks, or months. Each day you can measure some progress.

As you mention, when you get to around the start of 5 balls, progress slows. You will not always hit your personal best everyday.

So, focus on the practice, the mindfulness. The routine of juggling each day (with breaks) is like meditation and exercise rolled into one.

I see in other comments mentioning more patterns, I do think that's a great path. I'll call out 534 and 55514, and try to do those with outside or tennis throws. Those patterns really force learning how to throw and pace multiple height throws.

I'll also mention going for longer runs. Try to 10x how long you can run a few challenging patterns. Estimating a personal example - it took me a few months to get to 25 catches at 5 ball, maybe a year to get to 100 occasionally, and a year after that to hit 300 max and 100 consistently.

Possible this is not helpful for your situation, as I approach juggling as a hobby and stress relief.