Well, that's a really tricky question because, ultimately, it's all about what you're hoping to get out of it.
So, the more musical theory you know, (potentially) the better your composition will be, along with free style playing, transcribing existing music etc. But, there's no magic bullet, one size fits all solution, it's a personal journey. I think the more you understand the music you want to play, the more you'll recognise the theory which suits your needs.
Sorry I can't be more help, but all I can suggest is, try out a new scale then play around with it. Stick on a drum beat and play around with the notes, just grooving over the drums. If it doesn't work for your jam, bin it and try something else. If it does, focus on different roots or mixing with different scales.
The thing is, no matter what you learn, any proactive playing is a forward step and will improve you as a bassist.