I would not say that clam are maintenance free. They will soak up calcium and alkalinity like you wouldnt believe. I would suggest avoiding the maximas, they are generally the most sensitive, IME. Corceas are nice, but need a TON of light. Personally, for a first clam, I'd say go was a derasa, they are hardy, and can be quite colorful (although not the typical blue you mentioned).
Whatever yuo get, make sure yuor water is stable, and make sure you maintain your calcium and alk.