Go BIG, or Go Home!
Kidding. You have to learn how to sail, then decide on a size that you're comfortable with. I went from 23, to 25, to 34, and now 44 feet. We've peaked at 44. I'm starting to shrink now, so the boat's getting larger.
I started day sailing, racing, weekend cruising, weekly cruising, now four yrs away from live aboard. You could just dive into a larger boat. I know people who have, and have gone cruising for years. If I had the opportunity to leave years ago, I'd probably be out there in the 34 footer, having an adventure. However, there are advantages to gaining some experience first. Either route will be fun, so enjoy, and best of luck.
PJ