Welcome! I too have just returned to the game after many years away and also started with the original Spanish Main! Spanish are actually the ships I am missing most though from that set!
You can still get cards from a few places. Hills Wholesale Gaming just sent me a large order and I have a huge surplus now. Spanish Main, Revolution and Oceans Edge are all available and nice sets. OE brings in a bit of fantasy and new terrain which I think will make the game even more fun!