Just a reminder. If you're looking for etudes to work on your technique, try the Parker Omnibook or the Coltrane Omnibook.
They are great and saxophone doesn't seem to me to lay out easily on the vibes so the music is challenging. I have always thought that trumpet lays out really well on the vibes. Don't know why but it does. Maybe it's harder for trumpet players to jump around on the instrument? What do you think.
And if you use transcription books, you are working on improvising, even though the best way to do that is to transcribe it yourself.