Welcome to the site
I've moved this into the saltwater section.
Yes, you need to quarantine your first fish. If you get ich into your display tank, you won't be able to get it out without removing all fish for 6 or 8 weeks.
If you go for clowns and a few others, the clowns will probably be the last thing you should add, as they're fairly territorial for small fish. Are there any fish that appeal to you particularly?