Got the stones fae Leiths Quarry up in cove.They had a pile where you can pick out the ones you want.That bed ^^^ is appx 24m2 in area,by appx 0.5m deep on average.Used about 10tons of soils(A and M Smith,Portlethen give it away for free).Reckon I used uround 5 tons of rock for the wall.A lot of big eens hidden behind to support/build on,and small ones to underpin/ fill the gaps
If you canna be arsed with all that,I would have gone for sleepers instead,either horizontally,...or to give you more flexibility with shape,vertically. Some stunning pics in here among the dross https://www.railwaysleepers.com/projects/retaining-walls-with-railway-sleepers