First of all I would recommend buying a used one since you will get better value for the price. Also if you decide to stop playing you can still sell the bass for roughly the same as you bought it for.
The Knobs you are referring to are the tone and volume potspots (which is short for "potentiometers" or electric circuits that enable the attenuation of a signal to produce a change in volume or tone). Basically if a bass guitar has two pickups it usually has 2 or 4 knobs as well as a pickup selector. This will give you an almost infinite amount of possibilities. The tone knobs as well as the sound knobs can drastically change how your amp will behave for example. So they are not useless!
But, Still many people prefer not to use them at all, i.e. always using full volume and tone.
Others on the other hand like to fine tune their sound and hence mix with these. There are sound possibilities that you can't get to with any effect(a bit general!) without the tone knob.
What is more important than the number of knobs is the quality of the pickups. If you have bad sound from the beginning, no pedal will make it great.
So you should definitely go for a good bass and no pedal.
However a Bass with 4 knobs is not better nor worse than a bass with two knobs...