I like to stay into something until I feel I have a good grasp of it. So I would stay on modeling practicing for a while, at least until I feel I needed a change, then I would jump into sculpting, just to change things a bit and not get too burned out. That way I give modeling a rest and then after a bit of sculpting, jump back into modeling and keep practicing it. Because you are right, modeling is the foundation of everything else, and it also takes a lot of practice, so the point is to try and not get overwhelmed, and again, when you feel overwhelmed is when I would change things a bit and jump into sculpting.
I’d say do a mixture of trying to do things for yourself and when you get stuck then try watching a tutorial. But I’d say trying to model something from scratch without a tutorial is crucial for learning. Like ridding a bike with back wheels, it’s comfortable, but you need to start getting rid of them and risking a crash from time to time or you’ll never learn proper bike riding. And it’s ok if you get stuck or demotivated, we all have to push through it. Learning is not like in the movies where you have a passion and it never is hard, no, even if it’s your passion it’s going to be hard and you have to keep at it, because it does get easier and easier as you practice.
