For a first SW system, I suggest you do what industry does. Set up a small pilot system first, and learn on that before you invest in a large system.
When your doing this for the first time, you will make some mistakes. Sometimes they are major. It's a lot better to make them on a small system where it's an easy job to change it around or even tear the tank down. It's a massive job to do this on a large system. You will also learn a lot and not repeat the mistakes later when you set up a large system.
For example, one easy mistake would be to use very fine sand, and then fine the filtration and circulation system blows it all around. Replacing the sand on a small system isn't too bad. On a large system it can be an all day job. Same thing for livestock. In a small tank, it's easy to remove a fish, even if you need to take all the rock out. This is almost impossible on a large system.
This small system will not go to waste. You can use it later for a quarantine system or to keep something that you can't keep in your normal reef.