That's too easy. Why should we give up our finely honed experience that has taken years to refine? That's the fun of the adventure, getting out there and not having or forgetting something you cannot live without or taking a bunch of crap and hauling it coast to coast and never taking it out of the package. It's not an exact science, everybody is different. I ride with a childhood buddy (we are 54 and 56 now) who rides an Hardly Ableson and he wears the same pants for 5 days and buys new jeans, underwear and socks at walmart as he needs them. He didn't even own a rain suit until I got a new one and gave him my old one. I could put everything he takes for a 2 week ride in my tank bag and still have room for a small dog. While I'm hauling 30 or 40 pounds of gear and sitting in a motel laundrymat for a few hours every few days.
I divide mine up into categories so that all 3 or 4 of us are not all carrying 3 or 4 of the same thing. Why take 4 compressors? I finally broke my traveling friends from stopping and taking a photo of the same thing I just did. If you are alone you gotta carry one of everything. Then it depends on where you are going, warm, cold, wet, dry, etc. I've got it down to a minimum amout of gear but I look at what I use at home and build a list. Riding gear, tools, spare parts, camping gear, clothes, toiletries, medication, misc stuff. There is no exact list for everybody but I have bought stuff on the road and I've also stopped at the local PO and mailed or UPS'd stuff home. The type of bike dictates what you can take too. The carrying capacity of your horse and places to strap stuff on has a lot to do with what you take. Ever see the Wingnuts pulling a trailer? I can pick on these guys cuz I've been there in their shoes too after owning 20 or 30 different bikes in over 40 years of riding. When my wife rode with me I appreciated the carrying ability of the Interstate. I sold it and bought a Ninja and found a tank bag and a tail pack was plenty for me. I got some soft saddle bags and I was living high on the hog. I did the dual sport thing with an XR650L and you really learn what you can live without. Gortex is great.
I could have made a long list while writing this mini novel but want you to experience it for yourself. My advice, money or a paid down credit card, prescriptions, cell phone and most importantly a SPARE KEY! Try getting 1200 miles from home and not being able to unlock your steering head. Call ahead or research what states allow what. My first trip to New York was scary when some bikers staying at the same motel found out I actually carried a hand gun with me. Don't do that, not in NY. A lot of states don't tolerate radar detectors and that can sting too. Speeding ticket, fine for having the detector and it got confiscated. I bet that trooper is still enjoying my $400 Escort in his personal car. And don't forget to pay in those honor system drop boxes in the NPS campgrounds, they appreciate it. Oh yeah and toilet paper, but I carry that in every bike all the time, trip or not. Most everything you don't have you can buy, just don't haul those souvenir t-shirts for the family the whole trip, mail them home and it leaves you room to get more. =)
Emdubya