Yeah, most people agree that the first four aren't very strong work, and some folks say he doesn't really get going until after the first eight or so.

If you check out the reading order guide at the l-space web, there's a track for "Watch novels." I usually tell people to start there, because those are my favorites. If, otoh, witches are more your speed, you can skip the early book (Equal Rites) and go straight to Witches Abroad; the little dotted line indicates a minor connection.