Last month to be able to go to Venice and combine the visit of the city with that of the 54th Biennale d'Arte which will close its doors on 27 November. Admission is not exactly cheap but I advise you to check the possibilities of having the reduced ticket a 16€ (IKEA card, CTS, ITIC, Coop and many other cards) oa 12€ just in case you are students or under 26.
Venezia, you know, it is anything but cheap, but the last time I was there I found an excellent solution for an overnight stay at cheap prices: € 22 (+ € 3 of the annual AIG card in case you don't have it, for a total of 25 €) in dormitory with breakfast on the island of Giudecca just one stop from S. Marco.
Venice hostel is a structure with many beds, security lockers, a large common room at the entrance that is also used for breakfast and a bar inside, open from late afternoon offering great prices, the bathrooms on each floor are large and clean divided between males and females. The view of the Giudecca Canal and San Marco a little further from the window next to the bed is priceless.
The city usually creates a lot of problems for people too transport, the prices are always very high (€ 6,50 for a single journey with the vaporetto) but for those under 30 it is possible to buy the Rolling Venice Cardthat with 4€ gives you many possibilities for discounts on culture / catering / shopping / leisure time and offers ideas for itineraries (among other things it lasts until the end of the year) but above all it allows you to have a subscription for 72 hours of transport for only € 18 (total € 24 instead of € 33).
Another sore point is what concerns the meals, as far as I'm concerned I found a good compromise between price / quality / location in a small room in a corner of Campo Santa Margherita of which I could not recover the name, the flaw is the owner is a bit intrusive. For a quick bite, between the Zitelle stop and the first recommended hostel there is one small pizzeria when cut where they make delicious slices.