Nations with good Shops
This article is purely opinion based.
Almost all nations have good shops, but don't visit random nations to find good shops, there are always a few nations currently known that spawn trap, a list of them can be found here.
Nations with good shops (By what they sell)
Nations that sell god tools (from best to worst.)
Outback (wood, all forms of stone.)
Numidia (one of the best shops in the game)
Svalbard (wood and natural materials)
New York (super wide variety + very good map art shops)