I would say upper fifties to lower sixties, but you also need to have a few moving pitches.

what level of college? if you are wanting to play at the highest level at a division 1 college I would say at least consistent at 59.

Speed definetly isnt everthing. I would say high fiftys though. A pitcher with good movement is alwasy more effective then a pitcher that throws very hard. Its a lot easier to hit a fastball then a ball moving all over the place. So my opinion is to get your junk pitchers down then get your speed up. You dont have to throw 65 or harder to go to a D 1 college. Theres a pitcher for the Chinese national team that only throws 58, the thing is she has great movement which makes her difficult to hit, just because shes not throwing real hard doesnt mean shes easy to hit.