Simple question: what to you want to sound like?
Think a moment about your answer. How clearly in your mind can you hear the sound you want?
Without a clear sound concept, how do you refine your sound as you practice? If the goal is not clear, your progress will not be consistent.
Set aside some time each day for listening carefully to music.
Don't do other things while you listen. Don't read or eat. Just listen with
full attention.
What music? Spend some time listening to great players playing in the style
you want to emulate. Listen to every detail of their sound: When do they breathe?
How much vibrato do they use? How do they begin and end notes? What notes
do they emphasize in each phrase? What liberties do they take?
Also, be sure to spend some time listening to a variety of music. Listen to other styles and other instruments (including voice!) Time spent listening carefully can do as much good as time spent practicing!
Set aside a little money each month in order to purchase recordings. Even if you can only afford one recording every other month, you can slowly accumulate an impressive collection if you keep at it.
Of course, it is essential that you have good music for listening. The best choice is LIVE MUSIC. Learn about local performance schedules, write them in your calendar and GO. Once you are at the performance, don't allow your mind to wander. Focus on the music. Perform it in your mind as you hear it on the stage. Be an active listener, not a passive one.