You've been watching Bobby Chiu videos.

Ultimately, it's whatever works for you. There is no right path. If you try something and it feels more like you're working than having fun (obviously, you'll be working either way- it IS work) then scrap it and try something else.

I find that working on things exclusively in isolation does not help me. If you're working on the human figure and you can only draw faces, it does no good to spend all your time studying arms, because you're not going to feel like you're doing anything if you're drawing parts of the body out of context. It's probably better to work on a bit of everything than devote a masterclass to one subject.

The important thing is to keep drawing. You need focus to get anywhere, but not so much focus that you burn yourself out.

You also want to start working on an actual project as soon as possible, if possible. Something that challenges as many of your weaknesses as possible. It's fine and necessary to fill your sketchbook, but if you're not doing tangible things that you feel proud of as often as possible, then you won't feel like you're moving forward (probably) and that can kill your motivation.

As far as spare time, creative energy generally works in bursts. Having more time is not always a good thing, because you can only get so much out of your studies every day. There's a mental block you hit after so long, and pushing past that is not generally good.

Work in periods of 1-2 hours (as many as you'd like, broken up by however much time you need to recharge). Watch tutorials with your extra time. You won't get as much out of it as if you'd been working and studying these things yourself, but it can help you get a better idea of direction.