Welcome to reef2reef. It’s a great place to learn and receive help. I suggest to go to new saltwater forum and read all the stickies at the top of the forum. It will really help a ton
Welcome to R2R! In a new tank, you are going to have some algae cycles that fish can help with cleaning both the rocks and sand. So look for herbivores like a Starry Blenny type fish that will clean the rocks. For cleaning the sand, look for sand-sifting gobies types, like the Gold Head Sleeper Goby. These fish will work for you doing some cleaning. Hope this helps a bit.
Welcome to R2R, you'll find a ton of good information here. Like sfin said, start by choosing what your goal is and you can build the rest of the tank around that.
Edit: Not sure why this showed up on my "recently posted on" threads on the homepage, as it's almost a year old now. Hope the build is going well!