Gaines attended Miami Central High School in Miami, Florida, where he was part of the same graduating class as teammates Rakeem Cato, Tommy Shuler, Durell Eskridge and Devonta Freeman.

[1] As a senior, he helped lead his team to a class 6-A state title, recording a second quarter interception which he returned for a touchdown.

[4] Gaines redshirted as a true freshman in 2011, after enrolling early in January 2011 with Teddy Bridgewater.

In 2012, as a wide receiver, he caught 11 passes for 172 yards and one touchdown, but missed the final five games of the season due to a suspension, his second one that year.

He recorded 22 tackles and a team leading five interceptions, and earned first-team All-American Athletic Conference (AAC) honors.