You have to choose every single Tate choice, there is only a few that arent obvious like looking around when Tate leaves you and learning teleporting cancel. With Gael you can choose "He probably doesn't need a stupid Leopard in his life" and not betray Tate. If you want a list of all of the actions you have to do here I used Fandom: https://lustshards.fandom.com/wiki/Tate_Foster
(scroll down to good ending options)
I know =w= What I said is that I already do every action that didn't betrayed Tate the 1rst time I played except the Gael one because I didn't thinked it would do, I didn't even thinked there would be sex and even less that it would be not sucking Gael's cock or I don't know. I'm saying that the choice between "abandon Gael" and "betray Tate" is hard for me (even if I played an other time for having the "not betraying" path) and I'm sure it can have a way that we stay close to Gael but without involving sex. Like being there with him and speaking, or if we must go to the sex part nothing that make the MC lose his virginity. Because even if I would not betray Tate having to make the choice that litterally say "farewell I let you behind" for Gael is hard... I'm not speaking about a romance between our character and Gael, just friendship.
