If you don't even have a destination in mind, then don't worry about the bike. If it has 2 wheels and it goes, that's all you need. Everything else is just the details.

My 3 tours of Europe were done on the same bike on 700 rims (Mavic's) Never had any problems with them and swear by Mavic. They weren't the rims the bike came with. Learn basic bike mechanics, read as much as you can, and then decide what's best for you. Also, if you've never toured before, I'd suggest starting out with a developed country. You're going to encounter situations in undeveloped countries which could ruin your trip if you have no experience behind you.