A general explanation for the Island and the major mysteries will do. I don't need details as long as the details can be figured out from the explanation.
For instance: the Island has superpowers and those explain why people can teleport, travel in time, heal, etc. It certainly explains why Dharma, Widmore, et al are fighting over it.
It would be nice but not entirely necessary to know why it has these superpowers (such as a chunk of Solaris-type planetary alien intellect crashing into the Pacific eons ago). Even rumors about this would be sufficient. Why would anyone actually
know about the chunk of Solaris under the ground, anyway? The one thing I don't want is strained over-explanation for the sake of the audience, which is what happens when characters are forced by the writers to know things they really couldn't.
The "superpowers" could explain why Christian, Charlie, etc are still bopping around. It could be because the Island can resurrect the dead or because its a nexus for various realities, and those are "different" Christians and Charlies. I
would definitely want to know which is the correct explanation. So if there are multiple ways to explain something, I expect the writers to guide us to the correct explanation, even if it's something less than a direct explanation.
The superpowers might also explain the four-toed statue. Some ancient Polynesian civilization worshipped the Island as a god (why wouldn't they?) and erected a statue. The four toes don't bother me - just look at the crazy Egyptians with their jackal-headed gods. Or the bizarre looking Easter Island statues. There don't have to be 50-foot-high polar bears roaming the Island in the dim past for the statue to make perfect sense.
I don't really need to have the Numbers explained. That can be extrapolated from the "Island has superpowers" explanation, if we assume one of the superpowers is the ability to alter the laws of probability. What would be good: some direct evidence that the Island has this power. Then the Numbers simply follow from that. No awkward over-explanation required.
I'd like to know who Adam and Eve are. It could be something simple like two dead characters, male and female, being left in the cave. How they became skeletons in the past can be explained by some sort of time travel/teleportation. But I want to know which two characters they are. My theory is Kate and Jack, but if the writers want to play a joke on us, it could be Nikki and Paulo.

Since Adam and Eve aren't a central mystery, I'd be cool with that being a joke.