In my opinion, the best way to learn
online poker is mainly to start with ranges. The first thing you need to learn is which hand ranges to play from each position. For example, UTG has a specific group of hands to play, UTG+1 has another group, and the same applies to all positions: small blind, button, cutoff, MP1, MP2, and so on. Understanding and correctly playing ranges by position is the most important foundation.
If you learn to play the correct ranges and apply continuation bets on the right board textures, I believe that alone is already enough to start being profitable at the micro limits. Of course, taking a beginner course, watching YouTube videos, and studying additional material helps a lot. Watching final tables and observing how the best players in the world play is also very useful. All of this can be learned through YouTube and free courses, and you can also invest in a basic beginner poker course to speed up the learning process.