Which gate that i should follower after landing at Hangzhou if i need to using Airport Bus

Don't worry. After arriving, you can easily find the boarding site according to the English signs at the airport.
From the airport to West City Hotel, you are advised to take take shuttle bus Wulinmen Line and get off at Wulinmen CAAC Ticket Office. Then take subway line 2 to Xialongwei Station, Exit B. Walk north around 200 meters to find the hotel.