I got my bird up a few ranks and have been playing about with the Chocobo abilities
From what we know, you get a maximum of 55 SP Points (at level 10) to spend on Chocobo abilities.

Your chocobo needs to be at a certain level to pick each ability and YOU MUST BUY ALL ABILITIES IN ORDER. This means you can't take a rank 3 ability without taking the rank 1 and rank 2 ones before it.

The higher up a tree you go, the greater the SP cost. Level 1 abilities cost 1 SP, Level 2 Abilities cost 2 SP (plus the 1 SP from level 1), etc. up to level 10.

Basically; if you buy all the abilities from one tree, it will cost you all your SP (at any level). So you can either "Fully spec" into one tree, or mix-and-match lower-rank abilities from different trees.

From what I can determine, it looks like going Hybrid is going to be the best option except for in very specific circumstances -