I think the best pitch is a fastball with sink. really tough to hit when it is well located.
I also like the cutter and slider but both would be too hard on the arm (at least if you throw them supinated like most do-I'm sure dirt can tell us how to throw them safely).
the changeup is a must have pitch of course.
I think walks are overrated unless you can run. If you get a walk and put the pitcher in a stretch, that helps, but the guy who walks and can’t run, most of the time he’s clogging up the bases for somebody who can run. – Dusty Baker.