Literally, the only 3 things you have control over are: deciding whether you are going to pick a coffer or not, using the appropriate skills at the right time and feeding your chocobo. Given however the astronomical price of grade 2 and grade 3 greens, your only realistic option is buying grade 1 greens until you get to P9.

These 3 things easily make the cut for the lower tier brackets but will not suffice once you start reaching the highest tiers, which is where I personally don't like how "Pokemon like" the whole chocobo endgame thing is. You have more odds of getting a shiny legendary pokemon than getting a foul, 17+ star chocobo with 2 non useless skills. The RNG is so overwhelming that I bet my monthly salary almost nobody's going to even bother making it to the real endgame of chocobo racing once they start figuring out how it is really like.