This is a discussion on Skills within the online poker forums, in the Learning Poker section; What skill is more important in Holdem: discipline in the range of hands you play, or the ability to read the other player?
In this game, many factors are very important. And in each discipline you need to have different skills. But it is very important to determine for yourself your strategy of the game and develop it. After all, we all play in different ways ...
So assuming that you have neither and are looking to gain one, I would work on discipline first. As you learn that, you will also get better at reading players and be in a better position to take advantage of the moments you spot a tell. It doesn't help to find a tell if you already lost all your chips playing hands you shouldn't have gotten into.
I believe stress should be placed first in the discipline in the hands you're playing.
When you try to understand why you play certain ranges from the correct position you start to understand what ranges your opponents can be playing with context to their playing styles.
Once you master ABC poker you then gravitate to try and understand the possible ranges your opponents are playing, you try exploitative poker when you mix up your ranges based on what your opponents are playing.
I can't see how you will master reading other players hand ranges without understanding why you should/shouldn't play a given range yourself.
Cat's in the cradle and the silver spoon; Little boy blue and the man on the moon......