It's unlikely that Jeff Thomas will ever be a star at the Division III level, with Starter potential. Which is not to saythat you can't turn him into a solid player (easier to say if you would post their skill levels), just that he's likely to max out before you can get him to a dominant skill range. You might be able to make him into a solid starter or good bakup, though. Your other guy has a better chance of reaching the levels you're looking for, but again, it depends on where he's starting out.
Some general advice I can give: Work on their Outside Defense early. You'll want it at or around Sensational while you're in IV, probably more like Tremendous-Marvelous in III. Jump range you probably want to have between Strong-Prominent in IV, Prominent-Tremendous in III. Jump Shot should be in the same ranges as OD, maybe a pop behind. Passing is very helpful and should probably be Strong+. Driving/Handling you'll want to have somewhere between Strong-Prolific in IV, Prominent-Wondrous in III.
This build would almost certainly perform very strongly for you, but I have no idea how acheivable it is for you. If you're starting way behind I'd say don't skimp on OD, Passing or Driving. You can get by with a bit less JS/JR and create a defensive stopper who will be great for your team.
Since Jeff Thomas will probably cap before you can really hit all of those benchmarks, I'd suggest getting his OD and Passing up if you can.
Single-position train whenever possible. Try to get an Advanced or better trainer with a manageable salary.
Anything more specific requires more information.