Prices are right, you are forgetting a hydrometer though (unless that was included in test kit).
You basically fill the tank up with mixed salt water, let it sit a day or 2 with all equiptment running to allow full reactions to take place, then add live rock. In a few (2-3) weeks if things are right you can add some cheap inverts such as snails, hermits. Once it is more cycled (a month or bit longer) and everything looks good you can try a fish to start.
RO water is purified water that is stripped of all the metals, phosphates etc that are in tap water. Usually people have algae problems or parameter troubles while using tap but not always. I for example, switched over to tap because I realized my tap is ok to use.
You could keep mushrooms, cheaper zoanthids without a problem under that lighting.