Hi, we're a group of 5 pax travelling to Hongkong in July.

By MTR, you can take Tung Chung Line from Kowloon Station to HK Station. It costs HKD 10 per person if you buy the tickets separtely, or HKD 9.4 per person by octopus cards. Then, walk to Garden Road Peak Tram Terminal.
If by taxi, it may cost around HKD 70 for each cab. Since each one can hold four passengers at most, you need to hire two. Therefore, you can travel by MTR to save money.