What bus should I take from HK International Airport to Hostel at Paterson St. ?

Upon landing, you can take bus no.E11 at Airport (Ground Transportation Centre), get off at Sugar Street, Yee Wo Street. It takes around 80 mins. And the ticket fare is 21 HKD per person.
After arriving, walk northwest around 90 yards to find the destination.

From Paterson Street, how will I go to Macau? What's the travel time and how much is the fare on ferry and bus or mtr?

You can take Island Line at Causeway Bay Station, get off at Sheung Wan Station, Exit D. Then walk north around 275 yards to get to HK-Macau Ferry Terminal. It takes around 15 mins on the way. And the ticket fare is 5.2 HKD per person.
There are many ferries that can take you to Macau. The schedules are from 07:00 to 23:59 with the interval of 15 mins. It takes about 55 mins. And It costs 164 HKD per person.

Last Question - Thank you very much!

From Paterson Street to Ngong Ping? How to get there and how much? If I ride on the cable car from ngong ping, will it take me there to the big buddha? Or does it have a different route?

Walk from Paterson Street bus stop to Causeway Bay MTR Station to take Island Line to Central. Head for HK Station through an unerpass and take Tung Chung line to Tung Chung Station. It takes 50min and costs 21.9HKD. Walk 3-5min to the cable car station to take the cable car to Ngong Ping. The upper station is next to the NP Village. Crossing the village for 300-500m, you can see the Big Buddha.

With bus transfers, you can also reach the Big Buddha, but it is time-consuming and complicated, so cable car is more convenient.