Where is the best arrondissement to leave in Paris?

All the center, 1 to 9 but the best are the most expensive.
14, 15 are good too and most cheap.
13 is the Asian quarter is good and most cheap.
If you have a law budget you need to go outside Paris, for exemple in Arcueil you have the RER B. You need to look in the website itinéraire ratp for see your transports time.