If it is a hobby then probably the most important bit of advice is that you keep doing it in a way that lets you enjoy it. If you feel you need to become better regularity (translating to quantity) is in fact important, especially if you're the perfectionist type.

Coincidentally I teach (medialab) at one of the most recognized art universities in Europe and have a MA of fine arts and my mother is a painter. In my judgement the most overlooked (or most underrated) skill when it comes to painting is perception. Being a good painter aside from the manual skill has a lot to do with seeing or being able to see, even if you're not doing figurative paintings.

Painting more and more different things can be a good way to raise your own perception skills. It is also important to revisit old works occasionally. Ideally you will immediately see what was wring (or good) with them, something you may have not perceived back when you did it. This is proof that you leveled up.