I didn't notice that anyone mentioned fire extinguishers. It's best to have 3 to 4 onboard. We have one in/near the bedroom, one near the entry door and another in a lower storage bay.
Most of us have enough extra dishes, pots & pans, cooking utencils, glasses, towels, sheets, blankets, pillows, tools, cleaning supplies, throw rugs, etc so go through your house and fill up the RV with necessities. As newbies its really easy to over do it. Load up with essensials, go out for a short trip then add on what you really think you missed/needed. Keep everything basic...you don't need enough clothing to last a month or enough dishes for 12.
I agree with other...camping stores have great items but you can find all the basics at any department store.
Keep your rig loaded with basics all the time to avoid unloading and reloading stuff...then you can be ready to go in short notice.