You dont write anything about what you do or what you weigh ?
Waves or freestyle or ?
Assume it is waves, as most with TT's would never consider a 5m2 (unless you are extremely light weight)
If you got a "pull" kite like the Evo or similar, you have to choose 7 and 6m2 (and later get a 5m2), as the 7-5 change is too big when having a low windrange kite (EVERY low end grunt kite is a low windrange kite).
But with the Rebel, you should be able to get away with a 7 and 5m2 - because of the bigger windrange (the Evo lacks - but much better for heavier surfers)