There's nothing much to do when you reach high levels. Im lvl 77 with 48K bp, and an f2p. When you reach that point, focus on timed events like SWB, Matsuri, and other events where you can get items to power up, and if you are not freezing your level, you can go all out with 9tails to get coins for your 8 inner gates and upgrading your treasured tools. During your free time, beat as many ninja exams as you can and ultimate training too to get magatamas. There is nothing much to do really and you will get bored over time, but if you feel bored, do arena, or you c*ways check how much scrolls you have saved every minute but dont be tempted to use them until they reach 300 and with seals rebate. Or, you can chat with your groupmates, or spar with them and share informations and praise each other. You c*so talk about your enemy group and make a strategy on how to beat them on Saturdays.

There is nothing much to do really, but be patient. As an f2p, we cant rush our power. But waiting is rewarding.