This will be a case of "Do as I say, and not as I do", because I'm terrible with sticking to the practice regimes I set myself to. But ideally, a good warmup exercise (I think I have a video on my fav, the Spider exercise somewhere in my media posts. If not, I'll link it) to get ya started, then I would work on my main goal for that session (so if my goal is scales, I'll work on those with a metronome - If you would like me to make a video demonstration to try and help you, lemme know!), and then when I'm done with that, I'll play something fun or just mess around, kinda to just chill out and enjoy playing. How long for? I guess that depends. The worst thing is doing it for too long and being totally burnt out. 15-30 mins a day is better than nothing at all.
But mainly, just make sure you're having fun with what you're doing!