It is very good that you have a coach as there is a large learning curve for marine environments. There is a saying in the marine hobby world, "nothing good happens fast in a saltwater aquarium". The context is a reminder that any rapid parameter changes can kill the entire tank very swiftly. We encourage keepers new to the environment to allow for a full year to bring your new tank to cycle (3 month minimum for an experienced hobbyist) and to get your "saltwater thumb". You will want to start with determining how much space you have, a way to protect (especially living in an apartment) that area from both the salt and the water.
Your primary hardware will consist of a display tank, a sump (where you will house your maintenance hardware), a stand sturdy enough to hold the display and sump (water weighs about 8 pounds per gallon), a protein skimmer, a full cover for the display tank, a pump to return the water from the sump to the display, filtration between the display and the sump and a form of power head to move the water inside the display tank. To house most of the animals we see available, a 55+ display tank with a minimum of 15 gallon sump (larger is better) is recommended. Look at the
Tank Buildout post at the top of the Tank Talk forum for links to some examples of configurations.
In addition to the mechanical/chemical filtration mentioned, you will need biological filtration inside the display. This is typically done with live rock and to some extent live sand. See the
Cycling a Ceph Tank post at the top of the Tank Talk forum for links to articles and discussions about cycling a tank.
To understand more about the typical animals available, see
my first octopus tank in the Octopus Care forum. The second post is a rather long monologue about the species most often kept.
For some thoughts on acrylic vs glass tanks (including some notes on apartment considerations), see the recent,
Thoughts on Seaclear tank for cephs post by Pyrosnowman (another new enthusiast).
Lastly, do a little reading in the Journals forum for some ideas of first hand experience. Many people are initially frustrated with the interaction (or lack of) they experience with the animals they keep. These are very short lived critters and have different personalities. It takes a full month for them to really acclimate to a tank environment and the initial traits usually change dramatically. Often appear "friendly" out of the box but then become totally recluse. The challenge is to train them to accepting you as something of interest. The degree of interaction depend upon the species as well as the individual animal.
This post and the one that follows reference a journalist's experience and observations on two different GPO's. The animals we keep are smaller and arguably less intelligent but the two papers point out how differently the same species behaves.