Anywhere near downtown virtually all of the good places are quite expensive. The good news is that there are many of them and they are quite fine indeed. Two I can recommend are Mott 32 and Ye Shanghai, near Central and Admiralty respectively.
My favorite meal of the trip was out at Sha Tin 18, in the New Territories Hyatt.
Tung Po Seafood, above one of the wet markets, is one of the remaining good and relatively cheap places on Hong Kong Island.
On the even cheaper side, I can recommend the general row of eateries on Hau Fook Street, Kowloon, especially the larger Sichuan place on the corner, no English sign but they advertise being a WiFi HotSpot, I believe you will find it if you try.
Cheaper yet, the protestors served some pretty good fried rice, which I believe was donated by a local restaurant.
In general, the way to go these days is to either ante up on Hong Kong Island or make your way out to New Territories, or maybe try Kowloon City.