Hi Shelal,
Bennachie is a great hill! If you want something a bit longer, try climbing from the Don View carpark at NJ 673190 and climbing Millstone Hill first before descending to the Heather Brig between Mllstone Hill and Bennachie, then up to the Mither Tap. For the return you can descend back to the Heather Brig and follow a forest road around the west side of Millstone Hill back to the car park.
I'd second Rickamila's suggestion of the Correen Hills - a super walk with a steady ascent; you stay high on a broad ridge with some great views.
Or how about Morven from near Logie Coldstone? A fine walk, but once the snow comes it does tend to collect a fair amount and can become quite icy.
Or, Clachnaben from Bridge of Dye? Nice walk in and another distinctive top
Or perhaps Ben Rinnes - a bit higher and the same remarks as for Morven
All good walks and there are so many more locally
If I can help with info or anythig else, just drop me a PM
Kind Regards
Ian