Hi dogmom, I was lucky enough to have many good friends who live in Europe where I stay for free. They serve me with delicious breakfast and dinners. Hotels, travel, food can be expensive in Europe. In one situation where I don't have friends in Paris, so I found aparthotel (apartment-hotel) through google so I can do grocery shopping (do research to see if that aparthotel is closer to any food store) and cook at aparthotel instead of hotel + restaurants for 5 nights. That saves me a lot of money. Lunch+drink cost me $10 in Paris....I couldn't resist crepes...yum!
This is what aparthotel in Paris looks like:
Most of the flights in Europe are cheap, $13 to $100 through easyjet, ryanair, wizzair, and try to avoid large company airlines like Lufthansa, Delta, United, etc. and the price are usually go high during the weekend.
You will need to carry on bags, because they will cost you $50 for luggage. In Poland I rented a car for 5 nights for $110 which include GPS (it is a must!). I would recommend you to rent a car if you plan to travel across its neighbors..for example renting a car from Cologne, Germany to Brussels, Belgium, to Amsterdam, Netherlands takes you about 4 hours, and then drop off car in Amsterdam, fly from Amsterdam to Paris cost you about $25 (if you use carry on luggage, if not, $25+$50 luggage).
Flights from Dusseldorf to Paris cost me $13 through easyjet. From Krakow, Poland to Dusseldorf, Germany cost me $22 through Ryanair.
There are a lot of things for you to see in Europe...museums, attractions don't cost that much except Disneyland in Paris