The two best pieces of advice for this question is:
1) Camp one night in your driveway (that doesn't really address your hose question).
2) Make your first camp sites close to a "Wal Mart" or whatever as you will need to get lots little things to get set up.
I tend to disagree with folks who list lots of things you MUST buy- you may not need everything they list- even though their lists are valid as what a lot of folks wind up getting. I have two water hoses, but rarely use both. I also have a 20-ft sewer hose, and do need it a lot- because my sewer hook up is at the very very back of the camper...if that hook up was more centered, I might still have only a 10-ft one. I got the genuine 30A extension cord recently...have yet to use it :-(