If you feel like travel independently through Asia and doubts between choosing an agency or doing it for yourself, I recommend that you leave stories; Fill your backpack, get your vaccination arm and get a ticket.
It is very possible that through an agency you meet very interesting people and visit authentic sites, but only touring other worlds you will pay a third of the agreed price and you will be yourself who carries the guide, the map, the desire and the tempo. Not to mention the unforgettable experiences that will happen to you and the people you will meet.
I left Barcelona with flight to Bangkok. It was an open return rate of six months that rose to more than 900 euros. I did it to leave calmly and know that the return was in my hands and did not depend on other factors. Perhaps if someone had asked me the day before returning if I agreed with such a philosophy I would have responded negatively and had chosen to buy a one-way ticket and return by any land route without regard to time or borders.
I put on 600 euros in your pocket and I toured Thailand, Cambodia and Vietnam. From there I started to pull visa since the euros were over. I was changing bills in any bank little by little until they disappeared from my fanny-loincloth. Both visa and electron visa work in Asia as long as you are in a capital or a city of magnitude. As a detail, add that only the visa works to take dollars instead of local currency in certain countries. At least in Vietnam.