This guide shows how the gem link works and what blessing an item looks like.
How blessing equipment looks like
Keep in mind that the gem comination in the picture is just to show what it looks like, the stats on the bow is not the result of the combination of these two gems.
The amount of gems in this picture is 50 in each slot because the level of this character is 50.
If you are lets say level 34, the amount of gems in each slot would be 34.
You can bless an item as many times as you want but the next time you bless an already blessed item it will be overriden. So make sure you bless the item with the combinations you want.
To maximize a stat on an item you would need to combine two gems in all the slots except the lonely slot.
There is one slot that cannot be combined, this slot gives a raw stat. If you put a red gem inside it will give you damage.
Gem Link Combinations
You need to unlock the “bless gear” feature before you can do this. Just play through the campaign and you will eventually unlock this.
A link gem (orange small triangle) needs to be put in between the gems that will be combined.
Red = Damage
Orange = Damage
Blue = Health
Green = Health
Red + Orange = Armour piercing
Blue + Red = Critical damage
Green + Red = Critical Hit chance
Green + Blue = Armor
Orange + Blue = Maximum energy
Green + Orange = Counter-Attack damage (like thorns)
I hope this helps, i had to experiment around.