>>530920485
Power and speed are the most important I think. From what I've heard Guts doesn't actually do anything, but I really cant' say for sure, but from what people kept saying it's bugged stat or something.
Personally I grab the weather running skills if I'm not confident in the next race but I think I definitely got lucky with the Long Shot skill since it also gives you a slight boost if you're under 3rd favorite.