Whether it's Jazz, R&B or Gospel improvisation that you want to improve upon the best thing you can possibly do is practice everyday. Many think of practicing as drudgery. That doesn't have to be the case. If you choose a song that you absolutely love and practice the improv skills of the singer on the recording slowly and methodically you will notice improvement and you will feel good about the time spent practicing. Take it 4 bars at a time for 20 minutes a day on some day