To the Peak:
take Tusen Wan Line from Mong Kok to Central, exit from J2, walk along the road sign for about 10 minutes, you will get to the cable car station of the Peak.
To Ocean Park:
take Tusen Wan Line from Mong Kok to Admiralty, transfer to Bus no. 629 to Ocean Park.
To Langtau Giant Buddha:
take Tusen Wan Line from Mong Kok to Lai King, Transfer to Tung Chung Line to Tung Chung, and then walk to the cable car station of Hong Kong Ngong Ping 360(https://www.travelchinaguide.com/attraction/hongkong/ngong-ping360.htm). Take the cable car to visit the Giant Buddha.