No matter what limit you play on, the best way to build a bankroll is to have an advantage over most of your opponents.
There is only one way to improve your skill: play a lot and learn a lot.
Having worked with almost 100 low-limit students in the past, I came to the conclusion that the main barrier that prevents a person from going forward is ignorance of fundamental things.
You don't need to be the greatest poker player to beat microlimits. Not even close to necessary.
But you need a clear understanding of the basic things:
which
hands and positions should be played;
when 3-bet, and when just call;
what size of bets should I use on pre-flop and post-flop;
when to bet for the value, and when to
bluff on the postflop;
understanding how to take small banks from weak rivals.
And so on.
All these points are perfectly covered in numerous
poker books, articles and videos dedicated to playing at low limits. Poker forums, YouTube videos, and streams can also be useful when you're learning the basics. But perhaps the most effective way is to learn from a coach.
So there are many different ways to improve your poker skills. And it's definitely a good idea to spend (read "invest") some of your free time to learn the fundamental principles and concepts of playing poker.
This is because you will never start increasing your limits and you will never see your bankroll increase rapidly if you make basic mistakes at the poker table. And even if you manage to climb the limits at a very slow pace, at higher limits these disadvantages will affect the quality of your game even more, as your opponents will be more experienced and aggressive.