Salt water newbie

[Dearth]

I am a long time fresh water aquarist that is looking at setting up a salt water aquarium but have some questions.

-I have always been told to set up largest tank you could afford which has always stopped me cold from setting up a salt water but recently learned about nano aquariums And from reading various forums a lot of serious salt water aquarists dislike nano aquariums but I would rather take baby steps so what size of nano aquarium would you recommend 9, 10, 14 or 20 gallon?

-what kind of coral, rock, sand and bottom feeders/fish would you recommend for stabilizing tank and how many of each would you recommend?

-is darker setting better than having an aquarium in a bright area?

Thank you for any info you can provide