Has anyone found a way of buying metro tickets in advance? The stations are going to be manic, and ideally i'd like to have the tickets purchased before getting to the stations.
You can use two apps to plan your trip and buy various tickets. These are Bonjour RATP or IDF Mobilities. The type of ticket will depend upon the zones you wish to visit - CDG is zone 5, Orly is zone 4. The stadium is in zone 2.
It will likely be more expensive than buying on the day and using single tickets but if you want to be prepared and not queue the apps are helpful but complicated.
T+ Tickets are just City zone 1 so won't be much use. The Navigo can be purchased for either a day (selecting the zones) or a week (Mon-Sun only). Normally you would require a physical Navigo card from the stations which are then loaded with your tickets. However if you have a later Samsung phone this can be used to both purchase and validate tickets at the machine in the station using NFC -
https://alertify.eu/passengers-can-now-buy-paris-metro-tickets-on-their-smartphones/Both apps will require you to register. They will also make you download an app called Ticket sans contact which just sits on your phone and enables the tickets to work. One thing to note is that if you choose a weekly Navigo it will need you to add a picture to your account which is the same as the physical Navigo.
A zone 1-5 weekly Navigo is €22.80 but would expire Sun night. This will cover all the transport you might need (RER, Metro, busses) except specialist airport busses such as the shuttle that is needed from Orly to get to the RER line. CDG has the RER line anyway.
If it is too much hassle or the app tells you that your phone is not compatible, just buy what you need on the days you are there.