Good question my friend, yes, the water is the key.
I would add nutrient export is the key to good water, and of all recent hardware in the hobby, only protein skimmers remove nutrients; all others including your trickle filter, merely convert nutrients and stack them in your water. Most experts agree any marine fish system will benefit from a quality protein skimmer, consider adding one in the next 3 - 6 months. I notice you are primarily asking about fish health...in a moderate to robust fish population, some live rock is great, but it will likely decline over time, depending on species introduced. Keep in mind, mixing inverts and fish poses problems with curing cryptocaryon so be prepared for dealing with that if you are planning on keeping a serious fish population along with inverts. Adding a small quarantine system below your display tank will go a long way in improving your long term success.