As far as diffusion it is best to have a variety but as a wide variety can get expensive start out with 216 and 251 for color don't get crazy on faces at the most cosmetic rouge for light skin maybe straw for dark skin.
I like to permanently fix gels that I use over and over to flat aluminum frames others are happy to just clip to the barndoors of the light. You will get different effects from diffusion depending on it distance from its source that is my reasoning for the frames.
I don't think you will be very happy if you mix blue (CTB) and orange (CTO) on the face. Now, if you use one color one the face, say orange, and white balance to that and then wash the bg with blue it does have a good look.