Hello,Ms.ania
You can take airbus A21 from the airport to Dragon Hostel. It is an air-conditioned bus and cost HK#33 per person. Drop off at the 6th stop -- Mongkok MTR station. The bus takes aobut 35mins and you need to walk another 5 mins to get to the hotel. If you take taxi, the cost will be about HK$300 and the journey time will be around 40mins. So just use Airbus A21.