This is what worked for me playing banjo uke in an old time string band:
A D F# B (D (dog) is the lowest, A (my) is a full step (two frets) higher than B (fleas)). It's similar to the high strings on the 7th fret of a guitar, except the A is an octave higher than the guitar's string.
Metal strings for your banjo uke:
Jim Dunlop nylon .73 mm grey
Wrap your middle and index finger first knuckle with medical tape before you start playing. You are working with a cheese slicer.
Get an archery arm guard to protect the inside of your right forearm. Even if you have an armrest you'll get a terrible infected abrasion on your arm if you go to a festival and play all night without one.