a syth sound could be as simple as getting an octave pedal and turning the dry signal all the way down, and the octave all the way up! It all depends on the kind of sound you're going for, as you've described above. Personally, I think some compression (if not fuzz) is a must, as is an octave. Anything else is just an effect! That wasn't a very helpful reply.
when I want a "synth" sound, I roll off all my tone, turn all my dirt pedals on, and turn on an octave down harmony, oh and normally I would turn my wah on and leave it "up" so it's cutting top end.