You can try to find and hitchhike a sailing boat from Piraeus (Athens), other Cyclades Islands or Kalamata in Peloponnese. The chances are not so high and you'll definitely need a lot of patience and will.
If you are coming through Peloponnese, Kalamata will definitely be the best option to try your luck, having the largest marina (as also a good folks community and probably some of the most famous olives in the world).
Taking a ferry to Kythera from Neapolis is not very effective (though still ok if you are bored waiting too much and you have enough money) since on the island there will be much less boats.
Most of sailor depart directly.
You can theoretically blackride them, or at least pay half the ticket until another destination though won't be a very good deed. In some cases you can dare to busk ON the ferry (outside).
Crete is good for hitchhiking.
There is plenty of foreigners renting cars that often will pick you up even in most remote zones.
Locals as well tend to be very very hostful and kind, further than curious
Paying accomodation is usually a bit pricy, in the 4 mayor cities though, you have youth hostels for around 10€/night.
Wild camping is easy and tolerated (even if probably not actually legal) almost everywhere in the beaches, better if you don't set up the tent or set it off in the morning.
Cretan Nature is extremely rich in wild sage, figues, and other mediterranean fruits.
Oatflakes and dry black currants are generally cheap and good.
Good free wi-fi in many places, sometimes you might be asked for consuming.
A bit different from place to place but generally quite very rentable.
Cities and touristic destinations (sometimes small towns like paleochora or matala can be even better) are crowded by rich tourists that will fill your pockets of coins.
Crete is famous to be like Sicily in Italy, and several similar islands.
People are usually very tough, straightforward and respectful.
There is a very good culture of hospitality which though of course have been spoiled a bit by mass tourism. If you hitchhike/wildcamp/travel and live cheap though, people will understand your situation and intentions quite easily and will be extremely kind as interested.
There is a general tendency not to like very much the State authority and follow their own moral code and rules.
People do have weapons and grow weed, which though is all packed and sent to northern europe and almost impossible to find without being scammed.