hey Miguel,

don't know for the whole trip, but calculating on an average of ~ $500/month excluding expenses for international flights, (optional) insurances and expenses for maintaining stuff at home (bank account, remaining stuff at home(if any)). You might need less when going to Asia.
As labour abroad is mostly cheap, and wages are relatively low, the key is not to spend money, but work for food and accomodation, equipment etc., where possible.

Am currently focusing on Latin-America. So, at the moment I'll plan on going west - down to Spain, take a plane to Fireland and heading up north from there...

see ya,
Andreas