If you're just starting, the easiest way to get free stickers is by joining Monopoly Go communities on Facebook, Discord, or Reddit, where people trade duplicates all the time. Daily events and quick wins also give sticker packs pretty regularly. By the way, if you're interested in the Monopoly theme outside the mobile game, I recently came across this page about Monopoly Live. It explains how the game works and why it's different from the classic board game https://www.pokerlistings.com/live-casinos/game-shows/monopoly-live . I thought it was an interesting read.