Welcome and congratulations on your new rig!
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
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