I definitely prefer brewing in glass carboys, but I'd look for 6/6.5 gallon ones for use as a primary fermenter. The buckets work ok, but if they get scratched, that's a potential place for bacteria to hide.
My other main suggestion is to use liquid yeast if possible. If you can't find it in stores, check with local biology departments, sometimes they culture beer yeasts...
I'm kegging my wit beer today. So on tap after this afternoon are weird pink birch/wintergreen soda, grawk alt, and grawk wit