Hello,
I am in the process of buying my first travel trailer as well. Mine will take about 8 weeks to arrive, so I've been scouring the internet for all things related to being ready to use it for the first time. For things you should have in the trailer, I found this list very helpful:
http://www.thisoldcampsite.com/This_old_campsite5/Outfitting_Your_RV.html
I then started building my own list based on this one, some others I found on the internet, and just based on my own habits and what I picture my family will be doing on most of our outings. I've been going to wal-mart, costco, home depot, and building a long shopping list on amazon while I wait for the trailer to arrive. As I shop for some items I get them in my hand and realize that they may not be that necessary for the amount of space and weight they will take up, so I move on and figure I can always buy it later if I change my mind.
Good luck with your new trailer!
Don