Battle Arena Shop
The Arena Shop is available to players that have unlocked the Battle Arena (Story Mode Mission 4-6). The shop offers various Character Memory Shards and Equipment Pieces. The currency for the Arena Shop is "Arena Coins," which are distinct from "Princess Arena Coins" and are obtained from maintaining a certain Rank in the Battle Arena game mode.
Arena Coins are obtained from maintaining a particular Rank in the Battle Arena game mode. Coin generation is listed as Coins / Hour and range from 0 Coins (e.g. Unranked) to 50 Coins (Highest Ranks). Coins are provided every few minutes based on this rate, meaning a player's actual generation may change as their Rank moves up and down throughout the hour.
Players will also receive 10 Arena Coins upon a successful defense against an opponent in Battle Arena. A maximum of 50 Arena Coins can be earned per day in this manner.
A player needs to maintain a coin generation rate of 34 Coins / Hour in order to purchase one pack of Character Memory Shards (5 Shards) per day.
The following characters' Memory Shards are primarilly obtained through the Arena Shop. It is highly recommended to only purchase Character Memory Shards from the Arena Shop, as equipment is much easier/possible to obtain from simply clearing Main Story Quests rather than using the relatively precious Dungeon Coins.
Arena Shop Characters (800 Coins for 5 Memory Shards):
I recommend using your first Arena Coins on the following:
Recruiting Monika. If a player is unable to pull Monika from the Gacha, then recruiting them from the Arena Shop is an excellent way to guarantee recruiting them into their roster. Monika is an excellent PvP-oriented Support who can work with many different parties.
(Only after pulling Tamaki from the Gacha). Upgrading Tamaki from 2* to 3*. Tamaki's ascension from 2* to 3* is an excellent buff to her overall assassination power in PvP parties. The stat increase will also increase her survivability which can allow her to deal significantly more damage through a PvP round. It is not recommended (unless absolutely necessary) to recruit Tamaki through the Battle Arena, as the 7,200 Coins / 45 Shards needed to recruit can take a baseline 34 Coins / Hour player 15 days to obtain.