they are quite good, ayesha is on the... empty side though but its a good starting game to get used to the new system that atelier escalogy will bring next year.
for the ones we have id say start with rorona if possible to understand the concept behind it, and the characters and the story.
totri is #2 of the arland/rorona series so thats also a good starting point its alos very lenient.
meruru is the last of the arland series and its battle system and mechanics surpass the 1st 2 by a margin. i wouldnt advise starting with this 1.
they are good, it revolves around time management, exploration, raising friendships and doing quests and getting muliple endings.
i will also admit the games humor is prety nice, and no plot pressure ;nothing high end like saving the world or being the chosen 1. just an average life of an alchemist.