I find these quite easy to get:

Wedding chocobo and other Mog Station mounts
Collector's Edition mounts
Recruit-a-friend mounts / mounts bought with Gold Chocobo Feathers
The cheapest Gold Saucer mounts
Mount bought with Centurio Seals (level 50+ hunts)
Tradeable mounts on the MB
Palace of the Dead mount
Level 50 primal mounts farmed unsynced (level 60 primals have a worse drop rate)
Level 30 conjurer quest mount