6 months is a long time, but If I were you :
I would have started with greece and then go like this: turkey-israel--jordan -egypt-india-vietnam-china- japan-hong kong-singapur- thailand -indonesia-australia-new zeealand
bolded places dont need to be in that particular order ofcourse.
I wonder why so many people are set on Thailand Australia etc. Why don't 1st timers talk more about South America or Africa? I have been to Australia and Thailand and theyre both full of European tourists and - trying to be - trendy backpackers. What about Japan or Canada or maybe Venezuela and Vladivostok? Last time I was in Bangkok there were so many tourists there it was difficult to find a bar without a European or American. Not quite so bad in Australia but New Zealand is so much prettier and the tourist thing just isnt so harsh. I would recommend Russia to everyone. Moscow for a day or two no more, then on the trains to just about anywhere you like.
Thailand is punch drunk with tourists. Its a lovely country dont get me wrong, but it feels like close to home when you get on a train or bus or walk into a cafe or bar. Not really such a challenging adventure, more like a Benidorm in Asia.
I'll second a trip to New Zealand ..