Hi Marcelo,
Welcome to the forum!
If you can make it to a club meeting you can get all of your questions answered by experienced aquarists. Our next meeting is this Sunday in Wilsonville.
Good beginner corals are green star polyps, toadstools (sarcophyton), and Zooanthids.
I would recommend getting an all in one system if you are new. This way you don't have to decide what equipment to get along with the tank.
Innovative Marine, Waterbox, and Red Sea make some good all in one systems that size.
Cheers,
Andy