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)