Coral can be much harder to handle than fish. Certain corals need specific water flow, water temperature, pH, and the right amount of light for the right amount of time. Coral are also much more susceptible to sudden changes in water quality/temp/etc. There are some that are hardier because they don't need as much light, but they can be hard to keep thriving. You also have to feed corals certain foods and by varying techniques, so it can be difficult to make sure they're feed correctly.
If you want a simple set up, I would suggest just live rock. You can let a tank system establish for about a month or so with just the rock and then introduce some hardy saltwater fish. In my experience, clownfish are really good for this sort of thing. They're relatively cheap, they're pretty, and they're incredibly hardy. Out of all the saltwater fish I've owned, my clownfish have turned out to be the most resilient. Damselfish are also fairly tolerant and are even cheaper.
If you want to go super cheap on your fish, you can grab some mollies (they sell them as fresh water, but you can adapt them to being saltwater fish) to use as a way to test whether or not your tank is suitable for other, more expensive, strictly saltwater fish.