Since apparently we got namedropped I want to just note that the number of moves in the Collegiate gym roster is not just arbitrarily chosen! We fixed it at eight because doing so struck a nice balance between having useful moves for any single 'mon to use by itself, while also having moves that synergize with others in the roster. One particular consideration unique to our setup was "how can we ensure the RNG doesn't screw anyone over and give them a team that renders the challenge unwinnable?" and eight moves ended up being the magic number. Any fewer and we'd have to sacrifice on either the ability for any individual pokemon to hold its own and the ability create synergy and move combos with others. Any more and the movelist would start getting long to the point of making it difficult for a challenger to keep track of it all (a challenger is assigned 6 and chooses 3 to use; this means having to initially look at forty-eight moves and use a team with a total of twenty-four; adding more moves increases these numbers fast).

So basically, the trick to a move pool limit is to look at what you need to make things work the way you have in mind and then choose where to cap it accordingly, I wouldn't recommend just picking a number willy-nilly!