Here's the trick. I cheap sub or at $100 compressor will do the trick if you don't want to makeup all of the gain or go above unity -cheaper compressors get noisy quick at or above unity -The Boss CE and MXR Dyna Comp are the best in this category.
So if you doing basic compression on the bass and can increase the gain later (like at the amp) and it sounds good you are good
then you can get into mid grade stuff like the Keeley or JHS Whitey Tighty which are excellent -but purposefully lack some features for simplicity and are great
then you can get into high end like the Greer Lamplighter, Empress and Origin 1176 which are incredible but break the bank.
I suggest for bass just getting a decent one, or actually a $25 Behringer is tempting -I mean if it sucks it was only 25 -Lil Pigbacon, probably knows about it.