Would step foundation an option? You surely need to replace the clayey soil with compacted free draining subbase.

Yes,step foundation will work the best but too many steps will be needed to be built, thats my issue I am looking for some alternatives to decrease the steps number without sacrificying the structural strength.The contracter didn't come out with any extra thing need to be done for the subbase
like a compactable subbase like gravel.He believes it's not a disturbed soil so no compaction required for the wall base.I need to convince him to make a subbase,I think he doesnt have any concerns for the base taking into account the wall foundation width.It seems controversial that a base work must be done.Thanks for your comments..

I am with you on providing a well compacted subbase, unless you are founding on the rock, or informed by a geotechnical consultant. I think you can mix leveled steps with mild slope in between. I agree, too many short steps is not desirable.

You are providing very little information. What is the purpose of the stone wall? How long is it, 5 meters or 500 meters? You say the existing soil is undisturbed, but also say there are natural soil sets.

Considering the state of the construction industry in Turkey where there have been numerous failures over the years, if this project is a significant investment on you part, you should contact a geotechnical consultant for advice.

It will be a perimeter wall,just for property safety and nice looking for the land.It's about 500 meters long, 1 m stone wall below it, there'll be 50×30 cm reinforced concrete beam foundation and columns at 5-6 m long intervals.Natural soil sets is like 100 years old.The dry stone walls were built to retain these sets but now the old stone walls collapsed and there natural soil sets left.Will putting a subbase like compacted 5 cm gravel under concrete beam foundation do any job like stopping rainy water channeling under base soil or it is not an issue to think about.The land has a rectangular shape and the long sides has a 30-40 angle slope.
Will mild sloped stone walls with rc foundation beams above non compacted soil with a sufficient bearing capacity make any concerns after heavy rains.
To the wall contracter the soil is clayey at top but 50 cm below has a good bearing capacity to carry the wall load and the beam load so there's nothing to worry about