Dude feel free to ride whatever you want. Just make sure it's reasonable for a starter, like no gravios or deviljhos. Also Elder dragons might not be tamable in this RP. Not 100% on that tho. Also if you bring multiple monsters on a quest be sure to specify if they are staying out of the conflict. Because you can have at most 2 on a quest at a time, you could have more in total but only 2 on any given quest. If you had a gang or baby monsters just gank something into oblivion that would be a little OP.