Ok, back to the topic.
If u like to shoot high rise etc, then u can go to the Tsim Sha Tsui ferry terminal, this time the weather may be cloudy so u may not get those dramatic blue sky.
if u like colonial feel, go to Wanchai, take the green colour tram, the locals call them "ting ting" because the sound.
If u like to shoot beaches, then go to south of Hong Kong island, but the scenery is the same as any other beaches in other countries, so I do not recommend.
U can try to take a ferry to other islands eg Lantau Island, Cheng Chau Island, these are local fishing village and diff than the city scape.
Shopping wise, not much, everything is same or similar to Singapore, camera equipment may be slightly cheaper. If yr gf want to buy clothing, u should tell her now the seaon is almost end of summer and beginning of autumn, so many boutique are selling autumn fashion.