Gaines spent several years as a counselor for troubled youth in Alabama. She began her transition to racing when she and a few friends from Louisiana purchased some yearlings to break and train to re-sell the next year as 2-year-olds. She moved to Northern California in the mid-1980s, trained sales horses, worked as an exercise rider and eventually became an assistant to trainers Mike Harte and Mark Cuoto.
Gaines began her training career in 1989 with a tiny stable that got off to a good but modest start when Glory Quest won a $4,000 claiming race at Vallejo on the fair circuit. She moved to the Southern California circuit in 1996 and has 40 horses at Santa Anita. Harris Farms and Warren Williamson have had horses with Gaines since she took out her training license. Williamson, Gaines and jockey Joe Talamo all earned their first Grade 1 victories when Nashoba's Key won the 2007 Vanity Handicap. Nashoba's Key won her first seven career starts, putting Gaines on the map. The filly finished fourth, beaten two lengths, in the 2007 Breeders' Cup Filly & Mare Turf at rain-soaked Monmouth Park.