Sorry, but it’s ages since I hiked in Tung Chung area: many new buildings since.
I think that can hike west from Citygate, maybe check shore of Tung Chung Bay (still a pleasant old Hau Wong Temple by the bay); then look for trail(s) heading across old fields, towards the hills, and path up hillside past temple, and with views to ravine on your right.
This hillside trail still pleasant I believe; could also get there along road from Tung Chung. Maybe taxi to the old fort that doubles or doubled as a school, then walk on till a right turn at base of hills; or even taxi direct to this junction – Shek Mun Kap the location on map; buses pass there too.
Once at the top, you’ll see junction for new trail on your right: leads to circuit of hill to north of Ngong Ping. You could walk the circuit, or walk only the northern loop or shorter southern loop (not so wild as northern), then trail to near upper Skyrail station.
Hope this helps!