Farming

Gem farming
Gems Can be farmed in multiple ways, including through Glitches, going AFK on a reasonably long defend a point mission or by using the endless games.

Glitches
See Glitches page for more details.

AFK method
Leave some fighters on a defend the stronghold location (such as forest stronghold) for a few minuites, when checked after the mission is finished there should be a reasonable amount of artifacts collected. Repeat a few times to get as many artifacts as needed.

Endless method
Get a saint or another self healing charecter and run around an endless map without shooting any monsters and avoiding as much damage as possible, as the monsters stop spawning after a certain amount have been spawned. Even after the monsters should get more difficult, the monsters will reamin the same and allow you to run around freely without getting too much damage, you should also be able to heal yourself leading to being able to collect nearly endless artifacts. This works best on the final endless map (mushroom endless), but can also work on desert endless. Although it is best to take out the large sandman barbarians first before collecting any relics, as they can stun and can end up being deadly if unaware of them.

The colossus
the colossus can be easily and quickly farmed for both XP and coins quickly so long as you have either a 3 star Death knight, 4 star Master monk, or the necronon staff. Using these and a minimal number of fighters which you are looking to upgrade (as XP seems to be divided among members of the exhibition).