Ear training and then ear training and did I mention ear training.
THAT
and
Play as much with others as you can. Better players, worse players, players on your "level", who have a different (but ceomparable) skillset.
Every real life interaction / band situation with other players brings progress.
Why do I sleep away when listening to "modern guitar heroes"? Bc they are all elevated bedroom players.
By playing with others not only your skills grow. Your ideas also grow. And playing with others features one thing, that
@Eagle just said: Playing by ear. "What's that chord? This? No, sounds wrong. This? Nah..." and so on.
That said when I was young I should have played so much more with others. When I was 16 I had all the time in the world. And the others most likely, too. Now we are either stricken up in work or have kids - or both - and have no time.
Gear wise:
Cheaper (but okay guitar) --> More expensive amp. Not the other way round. I can stand a Squier, but I can't stand a cheap shitass solid state amp (the surely are good noes, though).