Start at the beginning - Season 1's the only thing you should bother with. In my scholastic opinion, and after deep meditation on the matter (there was a hilltop, there was Lion King-esque conversing with clouds), I think that the show went a downhill by season 2. It becomes more of a pick at random type of show at that stage, with the shifting relationships becoming repetitive & all over the place (not to mention borderline incestuous).

I think we all have our guilty pleasures. It's weird how I can know it's messed up and object to it, but I can't deny I get some enjoyment from it.