I always set "Any" to 3-6. I try to win minor league games to help development, so I want to get a good balance of useful org filler pitchers and position players. To that end, I also set SS/2B to at least 3 or 4, and 1B/3B/LF/RF to 1 or 0. Defense is very important in the minors, and drafting a bunch of shortstops, even if they can't hit, will help your actual prospects develop.