By the mid game, you can opt to run 4 Sorcerers to boost your damage. Annie can be any 4th Sorcerer, with an early Viktor being ideal.
Additional comp tips
This comp runs cheaper units at level 8 like Xin Zhao and Jarvan to try and eco to level 9. At level 9, you can drop Jarvan and Xin to add in Janna, Soraka, and Lulu. This will give you 6 Star Guardians, Mystic, and maintain Celestial.
Syndra will be a core carry in the mid game, so you can roll at level 7 to ensure you find her. After that, try to be as strong as possible while ensuring you can hit level 9.