Bran is posted at 11th, Here is my proposed progression till 20th:
12th: +2 INT, 2 new spells (Mental Prison, True Seeing)
13th: +1 proficiency, 1 7th level slot, 2 new spells (Mordenkainen's Magnificent Mansion, Crown of Stars)
14th: arcane tradition - spell resistance, 2 new spells (Plane Shift, Scatter)
15th: 1 8th level slot, 2 new spells (Illusory dragon, Maze)
16th: ASI-wis, 2 new spells (Mind Blank, Clone)
17th: +1 proficiency, 1 9th level slot, 2 new spells (Wish, Foresight)
18th: spell mastery, 1 5th level slot, 2 new spells (Shapechange, Prismatic Wall)
19th: Feat (alertness), 1 6th level slot, 2 new spells (Etherealness, Meteor Swarm)
20th: signature spell, 1 7th level slot, 2 new spells ( x, y)
Mike