Tenor banjos can be exceptionally versatile in terms of tuning/stringing, far more so than their longer-necked (5-string/plectrum) counterparts - here's just a few (pitches low-to-high):
- Standard (mandola) - CGDA
- Irish (octave mando) - GDAE
- Plectrum - CGBD
- Modified bluegrass (open G) - DGBD
- Chicago (baritone uke) - DGBE
- Drop-G tenor uke - GCEA
While prepackaged sets are available for the first two, you'll need to make up your own for the rest (FYI a standard plectrum set is gauged for a ~26" scale so you'll need something heavier); in terms of getting your feet wet, I'd recommend either Chicago or drop-G tenor uke to start, as the chord formations (and names, in the first case) are identical to the equivalent four-string guitar chords. My Deering Boston tenor is presently set up in drop-G uke, and I find it lends itself to the broadest variety of both musical genres and ensemble types, as it fills much of the range of mandolin/fiddle/5-string banjo (I've even fingerpicked it on occasion) - and the fact that's it's only slightly less loud than John Force's nitro funny car makes it my grab-&-go for chantey sings and Irish
seisiuns...