In my humble opinion, the best way of traveling over Provence is by car. Fly somewhere closer to Orange to Paris, for instance or Nice (in this case however, it's hard to drive away from sea…). Go further by train (TGV - 350 km/h) to Orange. Rent a car there and follow the inspiration or my picture and described places...
Hotels (Chambres d'hotes) cost no more than 200 francs per night, often even cheaper. Certainly after Provence, it is necessary to go to Cote d'Azur - there a lots of camping sites jet more cheaper.
If you find some relevant web sites, please send me links - I'd be glad to put them here.