There are only two cubes you have to worry about that will work on 99% of the units in the game: Resilience and Bastion.

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%
provides reload speed, which works on ANY unit in the game. More uptime shooting = more damage.
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%
is basically ammo “refund”, which works on most units as long as they don’t have a last bullet mechanic.
I would give priority to these two cubes for new players to at least level 7.
After that, you can take either of them to level 14. No need to go to max level (15) since you still get batteries on Solo Raid regardless.
Thankfully, we have a few cubes nowadays that are pretty good for endgame, mostly Solo and Union Raids.
New players should NOT worry about these until you have both Bastion and Resilience at level 14.

Piercing Cube
Piercing 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: 12Pierce Damage: 14.14%Damage as strong element: 19.09%
fills the niche of pierce characters like
Red Hood
Red Hood
and a lot more units in the current meta that can take advantage of this.
Destruction Cube
Destruction 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: 12Damage to parts: 31.9%Damage as strong element: 19.09%
can be used on ANY character as long as the boss you are facing has parts, since it increases the damage done to parts.
Rupture Cube
Rupture 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: 12True Damage: 14.14%Damage as strong element: 19.09%
fills the niche of true damage characters like
Ein
Ein
or
Chisato Nishikigi
Chisato Nishikigi
. Not as many units can take advantage of this cube, but it’s still worth considering to level up long term.
For distributed damage characters we have the
Diffusion Cube
Diffusion 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: 12Distributed Damage: 17.69%Damage as strong element: 19.09%
, and units like
Bready
Bready
or
Scarlet: Black Shadow
Scarlet: Black Shadow
can really take advantage of it.

Quantum Cube
Quantum 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: 12Burst Generation: 4.66%Damage as strong element: 19.09%
is great for burst generation on weapon types that are usually slow (SMG, AR, etc.) and also a popular option in PVP.
Adjutant Cube
Adjutant 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: 12Charge Speed: 2.12%Damage as strong element: 19.09%
can be used on any Rocket Launcher / Sniper Rifle that needs faster charge speed and it’s getting a bit more usage nowadays, but still not mandatory to level up by any means.
Vigor Cube
Vigor 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: 12Max HP: 9.69%Damage as strong element: 19.09%
is on a similar situation. More and more units can scale with Max HP which makes the cube decent for raids as a filler on some characters, but not a high priority for most players.