Relics

==How to farm "Relic pieces" and "Skill upgrade stones" efficiently==
# Upgrade all the masteries in the Assist tree. 
# Unlock and max all relics in the picture below (more relic pieces per return, starting at +x% stage after return, +X stage on rush, etc). 
# Use Rush as soon as you can.
# Use Return every 20 minutes.
# Rinse and repeat.
 Note: The number of Relics pieces received on a Return starts at 168 on stage 40, then goes up by 3 for every 10 levels you clear. Because it is a linear equation, you don't gain relics pieces faster the higher you climb. Thus, it is better to use Return as often as possible because lower stages will clear faster and gives relic pieces more efficiently.
 Thx to @Techno for this note.
Priority Relics - Patch 1.2.50 Update
=> Step 1 and 2 are to optimize your gain but you should do Rush & Return as soon as you can from the beginning. 
==Which Relics to upgrade first==
# Getting all the Relics up to rank S in the picture and get all of them to max level.
# Focus on all the Relics that give offensive stats like Attack and Crit. 
# Upgrade all other Relics afterwards.
# Repeat the 3 steps above once you unlock the SS Relics.
Credits
Edenlight & Nate
== No. of Relic pieces needed to acquire and level up Relics ==
Here you will find all the prices related to the game's Relic system (amount in relic pieces).
Rank 	Max Lvl.	No. of Relics	Amount of Relics pieces to max Lvl. (per Relic)	Amount of Relic pieces to unlock new Relic (total)	Amount of Relic pieces required to unlock Tier	Total [Amount of Relic pieces required to max all relics level] X [no. of relics]
C 	5 	5 	20 	48 	-- 	100
B 	10 	7 	90 	132 	50 	630
A 	20 	10 	380 	422 	250 	3,800
S 	30 	43 	870 	10698 	1,000 	37,410
SS 	50 	45 	4900 	54492 	10,000 	220,500
Total	 	110 	 	65792 	11,300 	262,440
* Total amount of Relic pieces needed to max out the Relic system is 339,532.
Credits
RyuJin & ZAGO.exe