SWEEEEEEEEEEEET new yarn... what to do, what to do?

I found some angora/wool yarn on clearance at my lys, which I did not have the will power to resist. I originally was going to make two hats and maybe a pair of gloves, so I bought a ball of white, a ball of this icy blue green color that I’m in love with, a ball of mauve, and a ball of grey (which is an alpaca-silk-wool blend from the same company). The yarns are called “Wings” (the alpaca) and “Lush” (the angora). I later decided to do a sweater instead, but I have no idea how much yarn a sweater takes. I bought another two balls of the blue and a ball of white. They are about 120 yards each and I’d like to do something in Fair Isle… which to me means that the mauve is an accent color and won’t cover any rows on its own, and the blue and white will have to overlap some. The grey I may use for the cuffs, or for a second accent color. How many balls of white and blue should I have? The yarns are worsted weight and I’m knitting a sweater probably woman’s large or so. Its totally delicious yarn, I hope I can afford enough for a sweater - its still expensive even on sale.