The same thing you practice in Lessons, IMO. At least the stuff that is decently consistent.
And a little more focus on the basics since those do often tend to get neglected, even if just a little, in private lessons since you are working on so much technical content.
Outside of lessons I taught myself Brackets, Rockers, Counters, Twizzles, etc. I experiment with new jump entrances, spin positions, and of course I go through the stuff that I do in lessons.
Ironically, while I hate spinning, I tend to spend a lot of time on them on my own than in lessons, and they tend to be better there (less pressure?).
Just keep on the status quo, and throw in a few things here and there to keep things "fresh" and avoid falling victim to monotony.