While you are levelling up and going through your breeding program to get a 4* P9 bird, just invest in Speed/Endurance/Stamina "evenly". By that I mean, if the auto stats give you speed, use either Endurance or Stamina food on which ever stat is lower. Only race Sagoli Road, as it is short / easiest track.

As for the breeding program, once you have a pretty good bird, P9 with 3* or better and Rank 40 or higher. Start doing the challenges. The challenges unlock your bird's top tier skills. e.g. Speedy Recovery III.
As for feed, Grade III food is expensive and can only be purchased with MGP. Grade I and II feed can be purchase with Gil or crafted with a Culinarian.
Once I reached P8, I stopped using Grade II Feed but I was making enough MGP from the rank levelling process to buy Grade III food without burning my MGP reserves to badly when combined with daily cactpot and challenge log bonuses.