Sounds like once you get the rig there, you are going to keep it there, so to initially setup, you'll need the sewer hose, white water hose, pressure regulator, maybe some boards to level with and for your stabilizer jacks. You should just be able to plug in your shore power cord to the pedestal with either your 50 or 30 amp plug no problem..
The rest just depends on how you wish to "camp" and what you wish to carry back and forth..
I've found that having a fully stocked TT with all the kitchen gear and utensils is essential.. Stock it so all you have to bring is food and clothes depending on what you decide to keep in the trailer.
We like to use "real" plates, bowls, glasses and utensils, so the trailer has it's own stock of these things. If you don't like doing dishes, then go for the disposable stuff. No big deal.
Since you own a good size boat, you should already know about the holding tanks.. Well, you comment about the "grey tank" means your boat probably only has a single waste tank, but the grey tank is for sink and shower water. The black tank is just the toilet.
Since you are going to take delivery and go straight to your seasonal site, I'd suggest bringing along whatever you feel you need and go from there...
Take a note pad and jot down the items you need or don't need for your next visit.. Continue this until you are comfortable.. Took us about 5 years to get our trailer fully stocked to where we like it!
Still always tweaking on it too... We've made mods to the trailer, which then adjusts the stocking of it... To this day, we do something new and say, "why didn't we do that earlier?" My one comment I always say as we are leaving, is "well, if we forgot anything, we can always buy it..."
This is our 15th year with our TT..
Good luck!
Mitch