Hi Fred. Welcome. Nice to see someone who wants to get some info before diving in. Your freshwater experience should serve you well. I think you should get an idea of what you have room and budget for and start there. Start big. Again, you probably know this already, but larger volumes of water are paradoxically easier to keep stable than small ones. Take your time and go slowly, but give yourself room to expand. As specific questions develop, ask them.
A refreshing intro, as opposed to what we see much more frequently (my pet peeve): the "I just bought a setup at the store, mixed water, put my fish in, and everything is dying! Why?" post.