Lisboa Viva Card
If you just moved to Lisbon and you are planing to use public transport daily bases, the best option is to get Lisboa Viva card.
Then you will be able to use any king of public transport within Lisbon Municipality.
The charge is less than 40€ and is valid for 30 days.
You can order the Lisboa Viva Card online here, however, all information is availiable in Portuguese only:
It takes 10 working days (!) to get the card.
It is possible to get it card faster, in 24 h, but that has to be done in person only, delivering the paper (which is also in Portuguese only), in one of the following metro stations: Campo Grande, Marquês de Pombal, Sete-Rios, Alameda and Oriente. This has an extra charge of 12€.