The camper will likely have a 30amp connection to allow you to plug into shore power. You can use a 30amp to 15amp adapter like this:
($10 from Amazon)
The amount of power that you can pull will depend on what you're plugged into. When you're on a 30amp site, you can usually run 2 high use appliances at a time (A/C + microwave for instance). When you're on a 15amp plug in, you're really limited to just one.
The generators would only be needed in 2 cases: 1) if you're camping without electrical hookups and you want to use your 110v power items (microwave, A/C, TV, etc.) or 2) you want more power than a 15amp connection.
As for absolute bare necessities, there aren't a whole lot of things needed to get out and give it a shot. You'll find you have a lot of "wants" as you get going, though.