Thank you. So we can add all of our rock and cycle our tank.. then later if we want corals we can add them? Or we can add them together?
We can't decide! Lol.. we're going to the fish store this weekend, then maybe we'll know what size we wanna stick with. We are beginners... and we want easy!
I wouldn't say the hobby is hard, but I wouldn't say it's easy either. If it's easy now, it'll be much harder later, when you have algae and bacteria outbreaks to deal with. Then you'll wish you did it 'right' the first time.
As Erin already said, if you want to go to a 55, might as well go with a 75. Chances are, you'll see how little room there is with your 30, and will desire more front to back space. A 55 is still only 12" wide, a 75 is 18". And she's also right that you don't want to cycle with fish, and don't trust your LFS. Your LFS might be a good one, but most of us have had really bad experiences with them. They want to sell you fish and corals as soon as possible for money. They won't care if they die in your tank, because they know you'll just come back to replace them.
Tank, water, heater, powerheads, sand, rock. A cycle can take two weeks to a month, depending on your live rock. If it's cured live rock from an LFS, then it shouldn't take very long. Use test kits.
After the cycle, do a 10-20% water change, and then you can add your first fish. I know it's hard, but don't worry about what you're going to put in it yet, unless those things happen to be an anemone or other sensitive corals. Most people recommend not getting an anemone for at least a year; by this time you'll know whether the hobby is really for you or not, and how stable your tank is. Anemones are kind of the unicorn in a lot of reefs, you need the best water quality and lighting available for them. If you want to an anemone later, then you'll have to take their needs into consideration now, by using the best water available from the get go. Lighting you can add when you get your anemone, but water needs to be perfect. I know I keep pushing it, but a RODI is the best decision you can make early on. It's as easy as hooking it up to a kitchen sink faucet. There are more permanent solutions, but it doesn't have to be complicated. Mine is hooked up the garden hose outside, for example, and I just let the waste water wash down the driveway. The good water goes into a brute trash can for storage. I'm going to hook it up to my washroom when winter gets here.
Take it slow, don't rush it. If you do, your beautiful vision of the ocean will turn into an algae farm. The more time you take setting up, the less chances there are you'll throw it on craigslist a year from now out of frustration.