I beleive you are able to get up to like 20 ranked players, however realistically you won't.
You want to make sure you get the best off the 100+ ranked players there's generally 1 or 2 guys 100+ ranked that are pretty good.
You can get guys 20-40 ranked with low we or a bad attribute that doesn't make them appealing to Big 6 like 70 red ath, but say 90+ reb/def/sb potential. Same with guards like 60 red ath but 90+ spd/per/bh potential. As well as these good ones with low WE or are ineligible.
Depending on the number of scholarships you can start to beat out a bad Big 6 team if you drop a lot of dough, although probably not till you reach C+.
Again while I mention rankings I mean good players in that area, as rankings aren't really that important but bad big 6 coaches focus on them imo over ratings, so it can help you figure out if you have a realistic shot while planning for recruiting.
It's hard to say what level of talent because it varies world by world, such as in Tark when I was at Yale it was very very tough recruiting, hardest by far, but I ran 6-6 superclass and was able to pick off low prestige big 6 schools and beat out other non majors for the best non big 6 talent. Whereas Knight while I did a horrible job coaching I recruiting pretty well and managed to suceed in finding high growth players wiothout a lot of battling because it was much easier situation in Knight than Tark.
Obviously you want to aim for the best at each position, its kinda hard to determine what ratings to go after specifically since you need to make sure you get good guards that have high bh/pas, make sure you have scorers, and make sure you have big men that can rebound. I think if you have 70+ ath/def you are good, but there is a lot of teams that do better without hitting that because their offense is incredible