1 year visa, do i need permesso?

The permesso di soggiorno is something that remains from an old Fascist law that was never abolished. The Visa allows you to come in and out of Italy whereas the PDS allows you to live here. Having said that if you don't need to work here and the place you are studying at doesn't require it then you might just forget about it. You might need one for stuff like getting a rental lease or even a monthly bus pass in some cities but if you can reduce your contact with Italian public offices you would be doing yourself a favour. The law does say that you should apply within 8 days but nobody really cares. Italian police are not going to deport you or even be bothered in the rare event that you should be stopped for a spot check. You would be treated like a long staying tourist and that might be good enough for you. If you have to get a document like the PDS I would suggest getting an Italian to go with you. Dealing with bureaucracy here is complicated. At times you need to be nice, at times you need to give shit. Knowing when it's time for one or the other requires experience.