What I found was that I over prepared and over fretted and carried too much stuff. Having done a few now I tend to strip down my seat bag and use a tiny one, only carry one tube instead of 2, ditch the pump and just take to co2, I don't carry any food that I don't get at a rest stop but always fill up on water at stops even if you don't think you need to (I was bitten at a ride than ran out of water at 80 miles stop in over 100 degrees, I rode past the 70 mile water stop)and I have never met a porta potty I didn't like. The last ride I did was a century with no halfway rest stop porta potty and I had to pee behind a car in a layby. When you are paying for a supported ride, enjoy the support. 50 miles will fly by though. Read reviews of previous rides, they often are useful. My biggest regret on my first ride was that my distance was too short.