Most companies have entry-level reactive balls that are good for learning to hook. I'd look into the Tropical Storm and the planet line from Rotogrip (Neptune, Saturn, Venus).
Laying out a ball for someone who is currently using a conventional grip (or throwing thumbless) is basically a crapshoot. You don't know what your PAP is, nor how it will change when you start throwing a fingertip ball. Your driller may watch you bowl first and recommend something. Or he'll put a label drill on it, with the pin to the right of the ring finger and the CG towards the grip center. That's a safe layout for the vast majority of bowlers.
SH