Let’s talk about the normal shop in NIKKE, what to buy, how to acquire the different currencies and most important, what to avoid so you can optimize your resources.
As usual, remember that all our guides are made for people who want to optimize their accounts, and you should always play first to have fun.

All events have a similar shop, and you should ALWAYS aim to clear them out when hardmode opens. After hardmode opens, don’t forget to buy the extra tries on the top left and farm
Core Dust
Core Dust Description An unknown substance that can be extracted in small quantities from a Rapture's core. Contains information related to the given Rapture unit's combat experience. Can be used to strengthen Nikkes. on the event itself, usually stage 11.
You can clear the shop even without the extra tries, but buying them with
Gem
Gem Description Highly-valued gems. They will never diminish in value even when the world meets its demise. means you will get, on average, 1 to 3 levels per event on your Synchro (depending on your account).

Core Dust
Core Dust Description An unknown substance that can be extracted in small quantities from a Rapture's core. Contains information related to the given Rapture unit's combat experience. Can be used to strengthen Nikkes. (if you can buy with
Credit
Credit Description Universal currency in the Ark. In short, money. , never with
Gem
Gem Description Highly-valued gems. They will never diminish in value even when the world meets its demise. )
Profile Custom Pack
Profile Custom Pack Description Collect a certain amount and use them to obtain a random Profile Card.
Credit
Credit Description Universal currency in the Ark. In short, money. )
You get
Union Chip
Union Chip Description These Chips are proof of a strong relationship. You can sense the strong bond just by looking at it. They can be used in the Union Shop. by doing Union Raids. You can also obtain
Cube Battery
Cube Battery Description A liquid catalyst used to interpret code from a Harmony Cube. It consist of numerous nanomachines, which physically penetrate the Harmony Cube. Can be used to enhance Harmony Cubes. doing Solo Raid when it’s available. A lot of people ignore cubes and just buy dupes of their waifus in this shop, honestly your pick since cubes will naturally level up over time thanks to the Raids.
Resilience Cube
Resilience Cube Description An unidentified cube with all kinds of codes jumbled together. It emits a special wavelenght that enhances a Nikke's performance. Main Stats Slots: 12Reload Speed: 29.69%Damage as strong element: 19.09% up until level 14
Bastion Cube
Bastion Cube Description An unidentified cube with all kinds of codes jumbled together. It emits a special wavelenght that enhances a Nikke's performance. Main Stats Slots: 12Ammo Refund: 3Damage as strong element: 19.09% batteries up until level 14
High-Quality Mold
High-Quality Mold Description Collect a certain amount of this item and use it to recruit SR or SSR Nikkes. Pilgrims, Over-spec Nikkes, and other specific Nikkes are excluded.
You get
Arena Exchange Voucher
Arena Exchange Voucher Description Arena vouchers for competitors to exchange rewards. Can be used in the Arena Shop. every day on your mail depending on your Arena rank and also every time you do PVP. This is probably the worst shop in the game right now in terms of what you can buy.
Profile Custom Pack
Profile Custom Pack Description Collect a certain amount and use them to obtain a random Profile Card.
You obtain tickets every time you pull.
Silver Mileage Ticket
Silver Mileage Ticket Description A shining silver ticket obtained when recruiting squad members. These luminous certificates are a testament to the sacrifices made by all Commanders in the fight to reclaim the surface. Can be used in the Mileage Shop. for normal banner and
Gold Mileage Ticket
Gold Mileage Ticket Description A shining gold ticket obtained from Special Recruit. These luminous certificates are a testament to the sacrifices made by all Commanders in the fight to reclaim the surface. Can be used in the Mileage Shop. for limited character pick up banners.

With
Broken Core
Broken Core Description Obtainable in coordinated operation events. Can be exchanged for items in the Recycling Shop. I would buy ALL RESOURCES and ignore the gifts. You get enough gifts and bonds everyday to now worry about those long term.
If you don’t have enough currency, priority to
Gem
Gem Description Highly-valued gems. They will never diminish in value even when the world meets its demise. and
Core Dust
Core Dust Description An unknown substance that can be extracted in small quantities from a Rapture's core. Contains information related to the given Rapture unit's combat experience. Can be used to strengthen Nikkes. .

The new currency obtained based on rank for co-op is
Rusted Bone
Rusted Bone Description A scrap metal that's shaped like a bone for some reason. Although it looks useless, Volt is very fond of it. Can be used in the Recycling Shop. . Important to note that you don’t get enough currency to clear this shop.
Co-op runs every other week while this shop resets weekly. If you are 10% in the rankings, you get 19,000
Rusted Bone
Rusted Bone Description A scrap metal that's shaped like a bone for some reason. Although it looks useless, Volt is very fond of it. Can be used in the Recycling Shop. , which would be enough for:
Curated Manufacturer Arms
Curated Manufacturer Arms Description Allows you to obtain a manufacturer box selection of your choice. , every 200 you get a gear selector
Elite Maintenance Kit
Elite Maintenance Kit Description A kit equipped with various maintenance supplies for maintaining different items. A kit tailored for elite commanders, containing tools that can potentially damage items if used incorrectly. or good teamwork boxesYou don’t get enough currency even at the top of the rankings to fully clear the shop, so be careful with this currency.