New to the hobby. Need some questions answered.

Thank you in advance for the help offered.

I am in the process of switching to salt and had a few questions on the whole process of setting up a new tank. I am aiming for a fowlr tank so keep that in mind.

A few stats first. DT is 90 gallons, sump is a custom made 40B. Return pump is running about 7-800gph to the main tank and ~200gph through the refugium section of my sump. Also have a koralia evolution 1400gph pump in the DT.

This is my plan on setting it up, tell me if I am correct or need to do anything differently.

I plan on putting 90lbs of base rock in the tank first. Since this is a new tank I will then fill it with RO/DI water and mix the salt in the system. Then I will add my "live" sand (yes I know, waste of money, but it was all that was available to me at the time). Once the tank is running I plan on getting about a 10lb piece of live rock to help seed the base rock. I have also been directed by fellow saltwater aquarists to use a product such as Dr. Tim's or biospira to jump start the nitrifying bacteria.

My main question is after I do everything listed above what comes next? Should I add a hardy fish at this point to keep the cycle going while the tank establishes? Or should I put in a piece of raw shrimp as some suggest as a source of ammonia?

I've also been told to not run my skimmer for a while as this whole process starts. When would I start using the skimmer?