Hong Kong Trip

Just look it up on the internet that helps

All the things your asking for vary by airline, the date you leave, the hotel you stay in, the food you wish to eat, etc. Etc.

This is research you can easily do online.

Hong Kong is a relatively pricey destination. Accommodation is the biggest expense, followed by drinking in Hong Kong’s bars. On a very tight budget you could survive on, say, HK$300 a day, but it would require a good deal of self-discipline. Better to budget something along the lines of HK$600
When you are planning your trip go , Public transportation are extremely efficient so you dont really need to ride in taxis. for 3-3.5 star hotels or simply guest houses, travel through MTR (metro rail) or buses are cheap.
Hong Kong is renowned as the world's shopping and dining paradise. You can eat like a billionaires, in the same token there're many affordable places with unbelivable prices. HK has the cheapest MacDonald's prices on earth. A Cantonese wonton noodle soup is only around HK$12 - 15 depending on location. A popular Chinese fast food chain all over the city, the De Coral Fast Food, with set meals under HK$30.
Hong Kong is a fun place to be in, there's always so much happenings around 24/7.
You can just search at google for the sites for cheap flight tickets and Hotels in Hongkong or you can simply visit a site like Yatra.com and book your ticket and itenary there. I have been using this site since last 2 years and I find it very helpful.