The most important factor in racing is weight and class combined. Can the horse carry the allotted weight, in this class of race, better than the opposition can do theirs.
2ndly can it do it over the distance. Some attention should be paid to stats at course and distance but only to look for descrepancies. ie Either exceptionally good or exceptionally bad records which defy explanation.
3rdly - consistency - go to inracing.com.au and buy this book for $2.20 (normally $15) it will be the best value for money buy you ever make.
4thly - Barriers and jockeys - they do matter but NO combination is so bad that it will prevent a superior beast from winning, however you must allow for likely bad luck or errors in your priceline.
Finally - the X-factor - secret!