Riders don't work in teams. It's a group of heroes who all have their own agendas. Ryuki and Gaim have had the most, with 12+. Though even something like the current Ex-Aid has at least six or seven.
Kamen Riders don't have teams, as they are usually fighting each other, but Kamen Rider Gaim had like 18 of them.
That really is a lot o_0