cheapest ticket for Paris RER and Metro?

i am 20 years ols and want to travel from zone 1-5 in paris via RER/Metro/tram on weekends.

what is the cheapest ticket available?

Is there a weekend paas also? By AJI used to communite from Paris to Cergy Pontoise for school, which was located in 5th Zone. If I remember correctly, Carte Organge (monthly pass) is around 120 Euro. It gives you free access to bus/metro/RER within 5 zones (both airports Charle De Gaulle and Orly are within 5 Zone). For one way trip, I guess it was 7.5 Euro.