Devo comprare l’Hub?
Hopefully someone who speaks Italian will join in. 
But the quick answer is that no, you do not need a hub. There are several Wi-Fi devices which work well with smartthings. Also some other “cloud to cloud“ integrations that do not require a hub.
For example, most of the Meross WiFi devices, including the smart plugs and smart bulbs, work with ST. Even the garage door opener.
download the smartthings app. use the + sign in the upper right corner. choose “add a device” and you will see many of the companies that have integrations with smartthings in your country. That doesn’t mean that all of their devices will work. You will still have some research to do. But it is a place to start.
I will wait now until we get some Italian speakers to join the conversation. but I hope that will help. 