I will soon be going to Paris for two weeks to improve my French. I will have to make one specific subway journey along one specific line (from my accommodation to the school and back) every day, and would also like to have the ability to move about the city a bit outside of that. What would be the best/most cost-effective public transport pass/card to accomplish this?
If at all practical I'd prefer an option where I can travel as much as I want during my time there for a flat fee (rather than pay per ride) because I'd find that a more relaxing way to travel (so I can just travel as much as I want without worrying that this trip or that plan is specifically costing me), but if such an option does not exist or is unreasonably expensive I would of course consider a pay per ride option.
(I'm 23 years old and an EU citizen, in case it's relevant.)
EDIT: the school is ACCORD École de Langues at 14 Boulevard Poissonnière, and my accomodation is quite a bit away from there, near the Parc de Bercy. I will be arriving on Sunday July 7 and leaving on Saturday July 20.