We had a great time travelling by campervan on the island. We only had 3 nights but wish we had more! As others have mentioned, download the park4night app for recommendations on where to stay! There were plenty of folks camping in May so I imagine it will get busier as summer starts. Gas has gone up in price (like in lots of places). You receive the tank full and have to take it back full. It cost us €70 for half a tank (€1.99/L diesel) to give you an idea.
As others have mentioned, the van is older and there are some things that are broken/not the cleanest. However it did have all the basic things we needed for our trip. I was impressed by the fridge. It was so cold it actually froze some of our things (not necessarily a good thing but others we have used weren't really cold).
Jesus' daughter very kindly picked us up and dropped us off at the airport which saved us a lot of time and effort!They also said we were welcome to stay in their finca (campsite) and let us use their toilets/showers (basic but appreciated after a few days on the road!) Overall a pretty great trip :)