The cheapest way should be airport bus A21 getting off at Man Ming Lane. Then walk about 5 minutes to your hotel in Shanghai Street. cost: 33HKD per person. Your hotel is very close to Yau Ma Tei MTR Station, you can take mtr to Tsim Sha Tsui then walk to Avenue of Stars fare 4HKD. Next two stops are Admiralty and Central. You can walk to Victoria Peak from both of them. If you want to take bus 15 or 15C, get off at Central. The big buddha is in Nging Ping. You should take mtr to Tung Chung first, fare 15.5HKD per person. From Tung Chung, you can choose to take Nging Ping 360 Cable car or bus to the Buddha. City bus is much cheaper of course. Remember Admiralty mtr station, you can take bus 629 at Exit B2 to Ocean Park, fare: 10.5 10.6HKD. Disneyland is also in Lantau Island with the BUddha. You can arrange these two places in one day. Get off the MTR at Sunny Bay, one stop earlier than Tung Chung, change to Special Disney line to Disneyland. Special Line cost 6HKD per person.
Hong Kong has complete transportation system and complete information online. Click the MTR System May. It is a time and fare calculator.