An excellent resource for developing our improvising is vibes player Gary Burton’s masterclass here. http://thejazzbreakfast.com/2013/01/30/how-to-improvise-all-you-need-to-know-in-one-brilliant-lesson/.
It goes into some advanced stuff but also has lots of refreshingly simple ideas that you can begin to apply straight away.
One of the points he makes is that improvisation is very much like talking and the way we behave in conversation, where there are ideas, exchanges and pauses. He also makes the point that many musicians fail to consider the depths of a song in terms of its underlying chords, melodic possibilities and scope for rhythmic variation.
Improvising is also about the chemistry between us and a song, and it’s as individual as our own human voice. It’s as much about what we bring to a song as what we hear in it. Think of Bob Dylan’s songs. Look at how blues songs were a vehicle for African Americans expressing the frustration and sadness of their experiences in the America of the late 19th and early 20th centuries, like the Great Flood of 1927 that led to a massive migration of African Americans to the Northern cities of Chicago and Detroit. Listen to Indian ragas, for example Jan Garbarek's 'Ragas and Sagas' album from 1992. All of our experiences, joys and sorrows, achievements and frustrations, feelings about life and the world find expression in our playing, it’s not all about instrumental technique alone. And we can make meaningful music in a simple 3 chord 12 bar blues, it doesn’t have to be Coltrane’s Giant Steps. Speaking of which, listen to Coltrane's 'Lonnie's Lament' or 'Alabama' or Cannonball Adderley's 'Work Song'. It’s really not necessary to play every lick, scale, chord or arpeggio at the speed of light in order to play meaningful and tasteful music. Decide what you feel is useful and valuable to learn at each stage, for you. Play stuff that best elicits your own musicality.