Consider taking a train instead of a plane to travel between countries. Ferries and buses work too. On both trains and some boats you can get a sleeper, saving the cost of a room for the night. If you're traveling to a lot of places, look into a pass.
Be warned (especially if you're leaving from an airport that profiles): carrying too little can get you pulled for extra questioning by multiple people. Allow extra time to catch a flight in these cases.