Many corals are photosynthetic and feed mainly on light. It should be in the top 3 of importance . Depending on tank size a very good protein skimmer is important if not needed. Most say 2X tank volume is what skimmers should be rated for e.i. 150GPH skimmer for a 75g tank. For corals and inverts I think RO
water is a must.If you live in paradise you might not need it but ???
Go sump and use a overflow that will not fail and overflow on your floor. Drilled tanks are the way to go but you can make or buy a nice overflow also.
Marine will rob your wallet so if you think you can budget and get what you want and have fun that may be as challenging as the actual keeping also....
1 light fixture will run you $100 [you need 1 per 2' of length of tank ], skimmer can be between $150 -$1,000 depending how carried away you can get. If you are handy then the DIY end of marine keeping can be fun..I build my own sumps and some reactors .
Live rock and sand will add up as 1lb per gallon of each is what many say is common...
Others will chime in on their experiences .