That sounds like fun, we kept an apple snail by herself in a tank. She did get really big, definitely showing where the "apple" part of the name came from. For a while, we kept her in one of those Wal-Mart storage tubs with no filter, and she was fine. So it's probably okay to go uncycled if you're willing to do plenty of water changes, but as was said earlier, cycled would probably be best.
The kind we had was a voracious plant eater as the websites say. We didn't know that at first, so we put some plants in with her. If we hadn't taken them out of there immediately, she would have eaten them all in no time. It was always fun feeding her, because you could actually hear the sound of her teeth ripping the lettuce. Kind of weird and cool at the same time.