Welcome and congratulations on your new rig!

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Your question is truly a personal choice but the basics are multiple items and there is a thread here that has all the answers, The title escapes me right now so please do a search for tools, essentials etc..
If I was getting a new rig I would get these items: most from Walmart or bargain store to save $$
2 25 ft water hoses and a 10 ft as well
A camco water filter it connects to hose between water source and coach(flush before use)
A water pressure regulator to reduce chances of blowing your interior waterlines from CG water pressure
25 ft Sewer hose with a 10 ft extension orange with quick connectors
5 pair of the thick dishwashing gloves and hand sanitizer to keep in dump compartment
RV Toilet paper and black tank deodorizer( I prefer oxyclean/ oxy something)
Lemon gray water tank deodorant
Basic tool set of wrenches, screw drivers, test light and multimeter,tire gauge, extra fuses
Comfy recliner chairs
aluminum 2x2 folding tables
Outdoor carpet/mat
Honestly there are so many items it would truly be easiest to go to your nearest campground and ask the campers to see what they carry, bring a tape recorder or camera or lots of paper!
Hope my short list helps and I'm positive many others will add to this
Ron & Wendy 94 Pace Arrow 454