I'm trying to work out what the best ticketing option will be for occasional uses of public transport in Lille. Say, 3-4 trips a week for several weeks, mostly within the centre of the city, mixture of buses and metro.
I know that in some cities (eg London or Brisbane) you can get a card which you load with money, then use on a pay-as-you-go basis as you travel. I know that other cities (eg Hong Kong) you can get a card you load with money that works for both public transport and small purchases. There are some cities where you can buy either a multi-use ticket or a booklet of single tickets at a discount, which can be used over time. There are some cities which sadly offer no sort of discount for occasional use.
So, for Lille, what's the best / available ticket option, for occasional public transport use?