There are so many variables to be considered and your poll question is very open-ended, so it is almost impossible to put a definitive "number of dives" or "experience needed".
There are some wrecks well within recreational limits that have no penetration that I've seen students doing as one of their BOW checkout dives. I recently was on a trip in Grand Bahama where I did two wrecks that were in the 90-100fsw range, but they felt more like 15ft reef dives. I've definitely had more challenging dives up here in the NE, but its all a matter of diver/training/experience/environment.
I'm at times envious of people who live in warm or tropical locales, but to be honest, we have some of the best diving in the world right here in our own back-yard, and it makes going on those excursions to warm, blue water places easier to handle and more enjoyable. :14: