I never been overseas.
So I don't have the best advice. If you're not a risk taker and don't think the tour will be worth the money, I say take the tour anyway. Why not? Its much better being in a country and sight seeing then roaming around yourself and missing the best things just b/c you're a newb @ it. It would make the money you spent to get over there worth it.
If you are low on money, I suggest do what this woman did.
Jennifer Figge 'becomes first woman to swim Atlantic Ocean' - Times Online
Literally swim across the atlantic, that should save fees just to get there. Take energy drinks and all.