How would you like to wear it? If you are looking for a large pearl to be worn on a long chain, then look at larger freshwaters, Tahitians or south sea pearls, since akoyas don't grow very large.
If you want a daintier size pearl to be worn on a shorter chain, then go for the highest luster you can, whatever pearl you choose, because it will be highly visible.
If you want a classic white round pearl, akoya luster will exceed that of most freshwaters-- and akoyas have a bead inside so you can definitely get one that is fully round. A freshwater may or may not be fully round.
If you are looking for peach/pink/lavender colors, then you want a freshwater pearl. Those are natural colors for FWP.
If you prefer other colors-- then look into naturally silver/blue akoyas (often in baroque shapes), Tahitians and golden south sea pearls.
Metal color is sometimes chosen to go best with the pearl. I would put a yellow gold bail on a golden south sea pearls, for instance, but probably a white gold bail on a silver/blue akoya. But that's just me.
And then there is budget for this piece. Some kinds of pearls are simply more costly than others. Generally freshwaters will be the least costly and south sea the most costly, all else being equal.
