I highly recommend taking a class. Te Wānanga o Aotearoa has free ones that are generally evening classes.
There are other places offering courses but you'll probably have to pay.
The TWoA ones provide the Māori made easy book (and the sequel in the second year).
For flashcards, you can use Ankidroid. It has downloadable te reo set, but I think it's better to start empty and add your own words and phrases as you learn them in other places (course/book/etc).