Pls. tell me the rides to take in reaching the following destinations orderly.Cheap&safe way.Thanks!

From the hostel to the park, you can walk to Mong Kok MTR Station to take subway Tsuen Wan Line and get off at Admiralty. There you can easily get bus no. 629 to the Ocean Park directly.
As for your second route, bus 6X, 6A and 37A can take you from one place to the other.
You can walk to Central MTR Statoon to take Tusen Wan Line and get off at Jordan MTR Station. Getting out of the station from Exit A, you can get to trhe Night Market.
From the hostel to the Mawan Island, you can take the subway to Tsing Yi Station first. Then you can take bus no.NR330 to Pak Lam Road, Layby near the roundabout, which is near where you are going.
To the airport, I suggest you take the same route to Tsing Yi first. There you can take the airport express to the airport directly.
Nice day!