It would have been good if you could have written where you are flying to. If you are flying to Schiphol (Amsterdam) then Paris is near to it. And you can even include Belgium to your second place. If you are flying to Berlin/Munich/Frankfurt (Germany) then also you can travel to Paris and either go to Netherlands or Belgium. It all depends on how many days you want to spend in each country. Two whole days is allright for Paris, if you have 3 then perfect. To see Brussels you need 1.5 days atleast and the same goes for Amsterdam. !.5 days in Amsterdam will include only the main attractions. Hope this is clear!!
Yes you can go paris to italy and in three days you can wander tower of pisa florence and venice italy all can be a day trip check out my profile i have shard the trip and then 3 days are enough in PARIS check my profile for my paris trip as well
Paris and Vienna.
Vienna is cheap. For example, a locker in a train station can be rented for 2 euros for a whole day. Breakfast on an average and I mean a wholly filling breakfast costs 3.5-5 euros. Its wholly historical and the views of Danube are breathtaking.