Prepare Drupal to be multilingual in the future
I think the best approach is something similar to your first one.


Install Drupal in English as defaults 
Configure your environment for multilingual at the beginning.
Enable Italian Language
Set Italian to default language
When you create entities(Users, Content types, Etc..), configure everything at the beginning. Otherwise you might forget things later.
Enable multilingual support only for other pages excepting admin pages @ admin/config/regional/i18n/select (Under "ENABLE FOR SPECIFIC PAGES" set all pages except "admin/*")
Then do everything in Italian for Italian until you need English language stuffs.


Good luck.