Free resource
Pleco
My notes
I made my own flashcard decks rather than relying on premade ones, and the extra effort of building them gave me more exposure to each word before I'd even tested myself. The on-screen drawing feature for character dictation practice is something I kept coming back to when I didn't have a pen nearby. Genuinely the app I used the most across the whole study period.
I had Pleco open on my phone every single day without exception. Beyond being the best Chinese dictionary available, I used the on-screen drawing input to practice character recognition on the fly — whenever I encountered a character I couldn't type, I'd draw it in and let the app identify it, which simultaneously reinforced stroke order. The custom flashcard decks I built inside Pleco became my primary vocabulary review system, and the act of building them meant I'd already had multiple exposures to each word before my first review session.