Japanese! I found Jlab's decks to be a great fit for me
I ran out of new cards on the beginner's deck within 3 months, and quickly started the patreon-locked intermediate deck, which I'm enjoying quite a lot!
Also on the side, I'm doing my best with a deck I found on here, it's a list of decks made out of cards from anime episodes
I'm afraid I don't, but a quick search on the internet leads me to believe the best one is the one featured on Anki's website which is AnkiDroid, an open source software!