I just did WTC 1 Prelude n Fugue in C Sharp Minor n Chopin Op. 10 no. 8 for my semester 1 exam.
For Prelude and fugue...
C sharp major, B flat major, A flat major, n G major from book 1 are nice, or D major and A flat major from book 2.
For Chopin I agree with le_poete_mourant
Op. 25 no. 2 is a good starter...or maybe you could do Op. 10 no 5, Op. 10 no. 9, butterfly....
Perhaps Op. 25 no 1 if you have a wide handspan - it's so beautiful !