Free Gems in Towerlands?

Free gems are veeeeeeeeeeeery hard to get a hold of in this game. You only get them whenever you defeat a wave with a boss in it (and it does not even give you much just with 5 or 10 of it). Alternatively, you can pick the "HOT" missions in map (usually from Exploration Islands or Caravan Loots) -- which are more likely to reward you with additional 10 Gems if you beat its challenge.

However, if the reason for procuring Gems is related to something that can be earned later for free in the game, (for instance leveling up your character or tower to three levels) there really isn't a point of obtaining it thru a Gem purchase. Rest assured, you won't be missing out too much on the game. Tower Skins that will be available when you get to Level 100 are probably the most important things that you can get your hands with the use of Gem. However, they do not come cheap. So instead of relying on the method to get free gems, you should probably take the Kings Package early in the game that will have 800 gems in it for only $5 (which is a steal). For this amount of gems, you can buy 2 Legendary Tower Skins, the Valkyrie Unit, and the Cannon Module!