when i first started playing bass i taught my self notes on the FB, then scales, which are super important and really not hard to learn, then modes (i couldnt tell you there names but who cares) that when my theory becomes very patchy..
Cycle of fifths still baffle me..why cant that penny drop?
I have started to learn Piano and it has opened up my world as far as bass playing is concerned...Knowing the chords which your basslines are based around does really help IMO..especially when improvising...
i still think as a bassist its much more important to be able to groove and have a good ear, than have great musical theory