We are in Greece now. Will be here for four months in total. As this is part of a 12 month trip we came the long way round via Norway and the Baltic States but we will be going back via Italy. It's a beautiful country, especially out of season when the hordes are not here. We have been wild camping throughout, but have come in to a site just for the Christmas period.
The food is great, the wine is cheap and the people are friendly. There is very little infrastructure here for motorhomes away from sites so you need to think about cassette disposal if you are wilding. Luckily the Greeks, unlike the English, do not seem to complain if you empty it in a public toilet, as long as you leave it cleaner than you found it. We carry a shovel as a last resort. Fresh water is easy, almost every village has a public water tap and the water is beautiful, especially in the mountains. In general the roads are pretty good.
The situation with wild camping is the same as Spain. You can legally park pretty much where you like but so called 'camping behaviour' is illegal and the police will move you if you start putting out tables, chairs, washing etc. We have certainly had no problems to date so just use common sense.
Park4Nights is the go-to app for Greece listing sites, wild camping spots and water taps. Autogas is sold in almost every garage so, if you have a refillable LPG system, you won't have a problem.
Enjoy