Hi, Fert1. Generally speaking, the Asian (long, skinny) types are more productive for me than the Italian (bell or teardrop) shaped ones, but I think which kind you plant depends on how you want to cook with them. The skinny one are well suited to ratatouille or stir fry or pickling and the fat ones are better for slicing and grilling or casseroles like eggplant parmesan. A couple of years ago I grew two Louisiana Long Green, the skinny kind, and those two plants alone produced at least 40 fruit, probably more. So if you're the only one eating them, I'd say two plants. And then again I've had the rounder ones like Rosa Bianca only produce a few fruit all summer. Why not try one of each shape and see what you like? And maybe try a couple of different colors.
For me, eggplant is easier to germinate than peppers but not quite as easy as tomatoes. I use short stakes or cages for my plants. Heavy fruit can pull them over and some taller varieties can snap in high winds. Once out in the garden, I think they're easy to grow. Not too demanding at all.
Have fun!
