Great question.
This is all a matter of opinion. Personally, if I had to choose, I believe the short answer is: Behaviour Of Others.
HOWEVER!
I’d say that’s only the case if you have a pretty decent understanding of probability.
For example:
It’s all well and good learning the behaviour of others and picking up tells, but that will not help you if you don’t understand; what they could have, what you block, how many outs you or they realistically have, etc etc.
This is what I love about the game. There are so many variables and nuances to take into consideration, if you want to.
In conclusion, I’d say the best way to play would be an even split of mastering the odds and learning behaviours. Keep studying, keep grinding, have fun.