First important choice can be found in the third chapter of this episode. You must decide whether you will forge a letter and send him in order to help your family or remain loyal to Margaery and finish her letter.
[Finish letter to ser Maynard] - You finish the letter for Margaery. You remain loyal to her.
[Forge letter to Elaena Glenmore] - You forge a letter for Elaena so that she can marry Rodric. You broke your promise to Margaery. This option is unimportant of you convince Elaena for marriage when playing as Rodric in fifth chapter of this episode.