Fencing
The posts you can usually obtain by asking around. Try local farmers. You want to use a hard wood. It is illegal to carry posts on a truck made out of local wood unless you have a permit. This is enforced by Foresta who also sometimes have posts to sell or can tell you where you can find them. You might want to consider painting the wooden posts with used black oil for prolonged preservation.
If the property is near the sea you will want to buy the better quality barbwire known as "Motta". This is more resistant to seasalt corrosion. If you want to restrict access to people crossing the property install at least 5 or 6 lines of wire.
You also might want to consider "Malla Ciclonica" coated with plastic with a low block wall as a base for a longer lasting solution.