Save up to get a shortwave radio. Listening to other nations on the radio has always been called "armchair traveling". Write to the big stations that you hear and a lot of times they will send you stuff in the mail. Start with Radio Nederland Wereldomroep (yes, they do broadcast in English, though they're Dutch) because they're easily heard and they send you cards and pennants and stuff, and they'll tell you about their country.
From Bolivia to anywhere, right?? You will need a lot more money than just the price of a ticket, perhaps more than a 14yo can earn in a short period of time. The very last thing you want to have happen is not enough money to eat, put a decent roof ever your head and buy a ticket home.
Study history and geography and languages while in school. In the meantime, watch the Travel Channel. Read books that are set in countries to which you'd like to travel. Get a job as a flight attendant when you graduate.
You have a few more years to grow up before you can travel far, but in the mean time, read! Reading is a very safe way to travel. I recommend that you complete your education and develop a marketable skill. I have done electrical work in seven countries on four continents.
Best thing to do is set a goal of someplace you want to go. Then research the cost of tickets, hotel, food and other expenses and then start to save for it. That's how everyone else does it unless you put the expenses on a credit card and then take forever to pay it back which is the wrong way to do it.
Everything costs money, even exchange student programs; once you get to where you're going, you'll need to pay for food and places to sleep and sights you want to see! Work a part-time job, save up your money, and when you get a little older you'll be able to go wherever you want to go. At your age, there isn't much to do anyway (you're too old for kid stuff and too young for adult stuff). You would be better off staying with friends-- you're old enough to travel alone, but to wander around a strange place alone will make you an easy target. Now is the perfect time to plan and dream, however~ get a notebook, and fill it with photos of places you'd like to go, and write about what you want to see. Good luck, sweetie <3