first 2 posts are why you absolutely need to do more research than asking us. if you noticed they asked more questions than you did...
first, you don't need a protein skimmer. some of the greatest tanks I've seen, run skimmer-less. pros and cons to using one. very much debated topic as salt mixes have evolved, and things like phosban and chemipure have come to market. that is an option that you will need to come to a conclusion for yourself, as everyone will have their opinion for or against.
second, the real first question is what do you want to have, and do you have the money to support that question. corals overall are extremely expensive as are the higher end fish. if you cannot drop money and are already looking for ways to cut corners, not for you.
next one, don't cut any corners. every single one of us have tried, and learn from that, don't do it you'll end up spending the money anyways.
next, they have lots of different types of setups, all-in-ones are fantastic starter tanks as you don't have to do much extra buying other than in-tank. really want to decide if you want to do something like weepee has posted, or do you want a biocube.
Something on that note, if you can go bigger, do it. save the money from upgrading and get as big as you can. ask everyone here, the tank is never big enough.
next, to start a tank, get ready to spend a lot of time getting it just right. first 4 months i had my hands in the water almost every day (OCD). if you end up going down the protein skimmer route, youll have break in time on that also taking monitoring. time crunch is why you'll see a lot of setups for sale at the end of the summer, people ALWAYS underestimate the time it takes to keep a reef going. heartache is part of the game too, don't get discouraged if something dies, stuff dies from a 1000 reasons, sometimes not in your control.
just food for thought if it sounded harsh, it's not, just gotta get your mind in the right place, because it will take a while before the tank is self-sufficient, and based on the very quick question, you need some tough love.
and welcome!