So... One is near Fortree city. I don't know if it's water stone or leaf stone. Everstone
is in the cave. I think stones market doesn't exist. I have some thunder stone, but I
don't remember where I found it.

there is a stone markets.... but on pokemon yellow and other older version only. but in
pokemon sapphire you can get stones by trading the shard(red, blue, yellow, green) to the
man on a house near (i forgot). the shards are mostly found on the sea floors, the spot
with messed sand so you have to explore.

The shard trading house is near modeseep + thats where i get my stones its hard though}:

You don't buy the stones. You collect shards and trade them for stones near Mossdeep.

you can buy the stones in i gym mart

gym mart does not exist.

Look under water with Dive. You should find a few shards. You may use the Item Finder too.
Then, while swimming, you will come across a house. It belongs to the Shard Hunter. Talk
to him and give him any Shards you have. He will then give you Stones in return...
-Rockemo