It depends on how you play. If you wnat Kimahri to be a buff tank that kills everything, take him down a combination of Auron's and Tidus' paths. If you want him to be accurate, go Wakk's path. If you want him to be a Magic user, use Yuna or Lulu's path. Thieving is Rikku's specialty, so add another one of those if you want.

I prefer sending him down Tidus/Auron's path. He's essentially a better version of both with more mana.

Max stats refers to having the highest possible statistics per stat. So this would mean 255 ratings (or close to) in the following areas: Strength, Defense, Magic, Magic Defense, Accuracy, Evasion, Agility, and MP (999).

Luck and HP are not considered core values, since having 255 Luck can replace Evasion and Accuracy when those two stats are at base values (the beginning values for those stats). HP can also go as high as you want, but it is very difficult to have 99999 HP without sacrificing other stats. Anything past 35k is superfluous (and even then, most people prefer 9999 HP with strategy). MP values past 999 are useless.