Rookie GPS recommendations

[Swlatiger]

I bought a used boat this past fall and its been lots of fun. It came with duel fish/depth finders, just stock low end lowrance models, but no GPS. I've been using my iPhone and it works ok, but I'd like to be able to set waypoints and track where I've been as well as get route info. I spend most of my time between Mermentau and Lacassine so most of the maps I've seen don't have detail on these areas... Any recommendations on what I need or what features to look for?