From my research (which at the top of this section, there are VERY helpful tips which you should take a look at):
There is no exact time frame in which your tank should be set up before adding anything. Once you add your live rock, you should add deli shrimp and let your tank cycle. Once you have 10ppm of NitrAte, then you can add your CUC (clean up crew). This is a patience hobby and you will have to take your time, otherwise you will spend alot of money you shouldn't have.
The average rule of thumb is 1 - 1.5 lbs of live rock per gallon of water.
The sand is up to you as to how much of a sand bed you want.
From my understanding, if you're doing a FO (fish only) tank, light doesn't matter. If you wanted to add corals, then you would need to upgrade.
I had 2 Rena XP3's when my tank was freshwater. The response I got was, you would have to clean them weekly if not twice a week. From my understanding, they are big on getting packed with uneaten food and waste, therefore they add more NitrAtes. What you want is a sump underneath your display tank to help with filtration.
I am unsure about what size heater as I don't have one yet and haven't researched that part yet.
Someone might come in here and give you better answers, this is just my understand through my research. My best advice is to research, research, and more research.
