First thing i'd say is it is quite hard to get a tone that will cut through the band mix when playing slap.
A good slap tone is always subjective, but i'd say most people will do variations of a similar theme - the "smiley face EQ" . Either boost bass and treble, or just drop your mids. I suppose it depends what onboard EQing options you have. Problem with this, to cut through the same way you may have to increase your overall volume slightly (because of the loss of mids).
What makes slap good, IMO anyway, is making it accurate. Its relatively easy to play a slap line, but playing your notes on beat, and finishing them (note letting open notes ring) is what neatens them up, and makes them sound crisp.
Nothing wrong with keeping it as simple octaves if that's where you're at technically, some of the best disco lines are octaves, but i would personally work on your timing. I think that's where you're likely to see the biggest "gain". Keep it simple, but keep it tight