The trick to "getting" the game is realizing you need to choose carefully which stickers you use at all times. That means don't force yourself to unload the crap ones if you need to use stronger ones, but don't overdo it either. If you play this way, and use the battle spinner as needed, everything clicks and you'll generally have a plentiful stickerbook even when engaging in battles frequently.
It's also not communicated well in the game, but the amount of battles you engage in directly affects the coins you earn not only during and after battle, but at the end of each level. Once you start reaching the better shops and the
stickers, you need those coins.
Sticker Star isn't without flaws, but most of what people consider flaws are actually just birthed by playing the game like an RPG. This is only an RPG in the loosest of terms. It's a resource management adventure game.