Grids(honeycomb)

I am considering purchasing a reflector and grids. The possible grid sizes are 10,20,30, and 60 degrees. Since each grid is 70 dollars (£35) which size(s) would you consider most suitable for use with portraiture both directed towards the model and as a background light. I have no probem with distance either model to background or to camera but am limited in width to about 8 feet.