The beaches from Inverbervie southwards past Gourdon, The Haughs of Benholm and to Johnshaven are sparsely productive of agates and jasper. The beach at Inverbervie itself is probably more productive than the aforementioned areas further south, and in my experience specimens appear to peter-out the further south you go. The best places to search are generally the areas of shingle associated with the confluences of the small streams that penetrate the coast occasionally from the higher ground to the west.
Inverbervie agates tend to be small, mostly ranging from 1cm to 2 or 3cm. They are mostly opaque and jaspy, displaying shades of orange, brown and red, occasionally as with the specimen below incorporating areas of white jasper usually in the nodule's centre. I have one larger blue-grey agate of about 5cm in diameter, that is highly waterworn and shows onyx banding. Areas inland from Inverbervie are historically productive, and farmland and the beds of small streams that sometimes also have associated small areas of scree are always worth investigation, but I have no experience of collecting in these locations and this information is mere hearsay.
The most interesting Inverbervie agates are those displaying carnelian colouration (that is stones with two tones of earth-browns and oranges and reds, occasionally including areas of white also.) The initial specimen on this page is an example of one of these stones. It is my belief that carnelian agates from this location display colouration unique to the area (specifically the bright, yet also pleasingly earthy orange and red, presumably a result of inclusions of copper)