There is an app https://play.google.com/store/apps/details?id=it.to.gtt.tomove&hl=en You can even validate with NFC. The app kind of sucks but it has been working for me for the most part. You can purchase tickets via the app.
For public transport I suggest Citymapper, official apps like GTT To move are very low in quality.
VISA and MasterCard are accepted almost everywhere. TAXI may not always accept credit-cards, when booking one be clear about your payment preferences.
I would rather bring a small amount (~100-200 Euro) in cash too , just in case.
There are several options:
1) Via this app (available only on android) you can buy single tickets (daily tickets via the app are cheaper than physical ones)
2) You can get a GTT card with a subscription. If you are a student or under 26 years old you get a discount, also if you are a student probably your university card already works as a GTT card. Furthermore a GTT card without subscriptions can be used to store digital tickets on the card, paying less for daily tickets.
3) If you are a student there might be a chance of getting a partial or total refund of GTT subscriptions
check on the GTT websites for more info or just go to any GTT official seller in Turin
Facebook! Sul marketplace o sui vari gruppi trovi un po' tutto..
https://www.facebook.com/marketplace/turin/?ref=bookmark
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P.s.
Io la casa l'ho trovata lì.
io invece che le bombolette uso uno di quei mini compressori appositi XD alla fine risparmi.
Cioè ti costa 60-70euro ma a forza di bombolette da 5-10euro ci risparmi! calcolando che io do una pulita una volta al mese... e che le bombolette spesso fanno condensa se le avvicini troppo!
I personally use this app. . It's alright, although the real time arrivals are only as good as the data provided by 5T, which at the moment is missing a lot of lines as the newer busses have had issues with position tracking.