Gems are used by Knights n Squires as a sort of premium feature currency. You can acquire them in many ways- by purchasing them, logging in daily, completing 6 Daily Quests, completing achievements, leveling up allies to lvl 20 (10 gems), repeating a part of your Dungeon Map 30 times (5 gems), completing the Story, collecting Story Cards, achieving certain milestones in the Raid (2-40) or certain Ranking Scores in the Arena (3-10) and achieving certain PvP Records (1-350). Sometimes you can also get a gift from com2us with a small amount of gems in it.

Use of Gems Tips
Refill Stamina (5 Gems)

Adds your maximum

stamina value to your current stamina.

(Current Stamina may exceed maximum

stamina i.e 53/50)

A bad purchase

Do not refill stamina with gems.

If you would like to refill stamina,

use only Friend points

Refresh Black Market (5 Gems)

Generates random items in black market.

Items can have properties.

(Only items up to current area)

A bad purchase because higher stats items could be achieved

in the Waiting Room of the 2nd to last stage

of Cloud Caste on the Third Island.

Draw 3*-5* Ally (30 Gems)

Chance to draw a random

3*-5* ally, 4*-5* allies are incredibly unlikely.

(Ally ticket serves same purpose)

This is a bad purchase as 30 gems is not

worth 1 3* ally. Unless you are incredibly lucky.

30 gems is 6 stamina refills.

The game also gives you enough

ally draws with arena and

raid dungeon rewards so this  

should not be a purchase at all. 

Draw 10(+1) 3*-5* Allies (300 Gems) Chance to draw 11 random

3*-5* allies, 4*-5* star allies are incredibly unlikely.

Also a Bad purchase because

the reasons stated above.

Purchase Gold (10 to 600 Gems) Exchange Gems for Gold There is a 7 stamina gold event

on Saturdays which gives a sufficient number

of gold that is a lot more efficient than this option.

Spending gems on stamina running

this gold event dungeon

is the best way to go about earning gold.