Band sizes and examples
A soloist is very intimate and the most background of all the groups. Guitar and piano make great solo instruments.
Duos are very popular offering more variety than a soloist whilst not taking much more space. Duos are often guitar and a wind instrument like trumpet, or piano and a wind instrument.
Trios provide a good variety in sound and can be good for dancing. Generally they will be guitar/piano, bass and drums or guitar/piano bass and a wind instrument.
Quartets offer the most flexibility and can easily provide music for dancing. If you are interested in jazz early on and dance music later on a quartet is the way to go. A common quartet would feature bass, guitar, drums and a wind instrument/vocals.
To get an idea of different styles and sized groups take a listen to some of the examples below.