I didn't know much about Milan before I visited but it has an excellent range of things to do on a budget if you're travelling on a low amount of money or inter railing. If the weather is nice I recommend walking as everything is an easy distance away and it's the best way to take in the city. Check out markets for good deals on snacks and save your money for visiting certain places. The Duomo can be appreciated from outside just as well if you don't have time to queue, and relax in a park too!
Insider Tip:Galleria Emmanuele II contains the best Gelataria, try their cinnamon gelato - you won't be disappointed!