Letter Quest: Grimm's Journey Remastered

Gems can only be earned in Story mode; enemies drop coins in Endless mode instead of gems. Gems are earned two ways: dropped by enemies or from gem piles. There is a gem pile at the end of every stage, and the longer the word, the more gems it will give.

I highly recommend purchasing upgrades towards getting more gems from gem piles right away, as well as buying the book that gives more gems from monsters. Getting these two first will allow you to earn gems faster to purchase more upgrades.

At first 25,000 gems will seem like a lot, but after spending 25,000 gems and buying every upgrade, I finished story mode with around another 20,000 gems, so this achievement should come naturally while collecting all of the stars.