hi Jam,
i think it will be better if u do it personally rather than with an agency it is just a waste of money..
as long as u followed all the documents stated on their checklist and u listen to some of the advises on here I dont see any reasons why u cant do it by your own. If we managed to do it and have our visas am sure u can do it too..
Btw, what kind of visa u plan to apply? Goodluck..
