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A trip like this is going to cost a ton of money. You really will need to save up enough money to live on for an entire year, which certainly isn't going to be cheap. I'd think $20k would have to be your starting point, and that's for a very very bare bones trip.

As far as the rest of the planning, you're at the fun part: the daydreaming stage. Really you just need to keep thinking of and looking for places that are of interest to you that you might want to visit. Even with a year, you'll never be able to get to everything, but the more you know, the more options you'll have once you are on the road.