where is a good beach in scotland to find nice sea shells?

You can get shells in Salcoats, but they are usually broken, there were nice ones in North Berwick, Oban, Moray Firth Beaches I.e Cullen, Banff, Fraserborough.

There isn't many to chose from in Scotland, only a few different kind of shells. the most common is clam shell and razor shells, you dont get many conichs shaped ones here, which are the prettiest.

Ganavan sands in Oban has some nice shells - mostly the pearly spiral ones but I think also more common ones like the blue mussels or limpet ones. You would probably be best to time it so the tide is out as I guess anywhere at high tide wouldn't have many around. There is also wuite a bit range of dried seaweed - red, green, black which would be nice to use as well. You could also try around the car park are at Dunstaffnage castle just 3 miles north of Oban or Tralee beach 10 miles north at Benderloch

When I was young we used to visit Burghhead on the Moray Firth.

There is a a beautiful silver sand beach running for a few miles. I remember collecting shells.

The Moray Firth is on the East at the end of the Caladonian Canal.

It might be worthwhile finding someone who lives there and has a web page before taking the journey.