I don't seem to have a set number of syllables I prefer to use after a one-syllable name. I think it depends on the cadence (not sure if that's the right term) of the first name. Not all one-syllable names roll off the tongue in the same way.
Girl:
Jewel Annika (I tend to pronounce
Jewel as two syllables)
Eve RavenBelle SonjaBlanche RhiannonGwen SapphiraJoan Xochitl
Boy:
Dale NaveenHeath RobinBeau PercivalClyde OwenHugh NormanJoel Zavier