The following traits are all very important, but I believe they go in this order;
Effort > Opportunity to learn and willingness > born talent > time.
I'd also like to add, since I don't think anybody else brought it up ( I might be wrong) , that the worst thing you can be is repetitive.
It falls into "going with the flow". Simply being able to drastically alter your approach to a given situation will make you much better.
One last thing; one of the first things you should do, after learning the fg basics, is learn which style of play you are best suited to. Example being that one of the best zoned players I personally know started out playing rundown. He sucked at it, no lie. Practically had to force him to try a zoner, but once he did it was an almost instantaneous level up.
I really do wonder how many "bad" or "average" players are simply not playing the right character for themselves.