Welcome!
A couple of questions which will influence my advice:
1. Is this your first SW tank? Are you experienced in FW?
2. How tight is the budget? Salty Brother is right, that it will get pricey.
3. Do you know what types of corals, etc. you want to keep? This will be the driving factor for your setup (lights, water turnover, need for reactors, etc).
Here is my general advice, however.
1. If you are setting up a 30g, get an Oceanic 30g "cube" rather than a standard "30 long" or "29 high" tank. When a tank is only 12" front to back, it is very limiting for aquascaping and tank placement. The Oceanic is 18" front to back.
2. Sumps have several advantages, but also make things more complicated. For a sump, you need more equipment (reef ready tank or overflow box, return pump), and there is a higher chance of flooding if things go wrong. However, a sump gives you more water volume, a place to put equipment (skimmer, heater, auto top-off, reactors), and can be designed to give you some refugium space as well. There is nothing wrong with using hang-on filters, especially for a tank that size. There are even combo protein skimmer - refugium hang-on setups.
3. Buy GOOD equipment, especially a protein skimmer. There is a reason that they cost more - they work! Most inexpensive skimmers don't work very well without significant modifications. For a tank your size, something like an AquaC Remora would be a good choice. Also buy a good heater -- cheap heaters are notoriously unreliable and if your heater malfunctions it can only take minutes to kill your entire tank. Go ahead and buy a good test kit, and a refractometer too (swing arm hydrometers are unreliable). Trust me, you eventually buy them anyway.
This is just a start. Once I know the goals for your tank, I can be more specific about stuff.
HTH!
Dave