Dominaria and Dominaria United are both fantastic limited formats, so this is a cube jamming together the commons and uncommons! The whole thing is about $60 as of this writing. The sets play together well mechanically and should be fairly balanced, since they reflect well-balanced draft environments, and the added cards are meant to emphasize what's already there.

Minus the ~2 lands per pack, which are mostly DMU for Domaine, the split between the two sets' cards is fairly even. 20% of the cube's cards come from outside DOM and DMU (marked with teal in the list). In addition to color balance, I spread the additions evenly, with 9 non-Dominarian cards in each color, as well as a relatively even distribution of gold and hybrid cards to cement each color pair together.

The goal is a good cube environment with as many viable decks as the card pool can support. The multicolor bent of DMU is there, but the mana isn't incredible, with no fetches or shocks. Only ~5 fixing lands per drafter on average should shunt half the table into 2-color archetypes with or without a splash.

Here are the archetypes:

Domain
Aristocrats
Kicker
Defender
Legends
Control
Persist Combo
Knights
Pump
Pendelhaven
Spells
Saprolings
Goblins
Yargle

Domain

This deck is mostly DMU tribal, since it's the most prevalent mechanic in that set and relies heavily on DMU taplands. No untapped fetches at common or uncommon, but Krosan Verge is gas. The Domain payoffs are centered in green and are otherwise well-rounded for each color.

Aristocrats

It's possible to build an Orzhov or Golgari aristocrats deck, but the mana is easy and the token theme in Selesnya works well with cards in both color pairs. Golgari saproling cards pair well with white token payoffs like Benalish Sleeper and Queen Allenal of Ruadach.

Kicker

This is both the biggest and least disruptive add. Kicker is in both DOM and DMU, but there are no payoffs beyond Hallar, the Firefletcher and Bloodstone Goblin. Roost of Drakes, on the other hand, was its own archetype in limited. Roost is good enough on its own in Izzet spellslinger, especially with the addition of Jilt.

Defender

This deck is pretty much copied and pasted from DMU with High Alert and extra mill support. It's possible to build defender mill without white, but the aggro version wants the critical mass of 3-colors worth of defenders with Floriferous Vinewall and Thallid Shell-Dweller in green or Blight Pile and Gibbering Barricade in black.

Legends

This isn't a particularly easy archetype to put together, but there are enough legends in DMU and Historic cards in DOM that it requires very little support to be viable. Hero's Blade and Hero's Heirloom are perfect with Valduk, Keeper of the Flame and Danitha Capashen, Paragon.

Control

There isn't much of a mill sub theme in DOM, but Coral Colony, Founding the Third Path, and a smattering of other blue cards are enough to get the job done. Planeswalkers and the best removal are in black, while splashing green or red respectively give access to recursion and ramp or removal and discard.

Persist Combo

I didn't intend to add combo as an archetype, but it came together mostly by chance. In Thrall to the Pit is not a playable card, so Murderous Redcap took that hybrid slot. As a Persist-ent goblin that returns as a 1/1, it triggers both Sigil Captain and Grumgully, the Generous, which were includes for other archetypes, and it sacs for free to either Skirk Prospector or Sling-Gang Lieutenant. The deck has pieces in every color but blue, but it only needs access to either red for Grumgully or white for Captain to go off. Renata, Called to the Hunt, Good-Fortune Unicorn, Juniper Order Ranger, a half-dozen 2/2 Persist creatures, and any number of free sac outlets could be included for redundancy, but since the power level quickly gets out of hand, I stuck to Putrid Goblin.

Knights

There are a lot of knights in both sets. Not a lot of support has been added, but cards like Knight of Grace and Knight of Malice want to be in the same deck, anyway. The curve is mostly low to the ground, but Arvad the Cursed, Syr Konrad, the Grim, and Syr Alin, the Lion's Claw mean there's plenty of top end for a midrange build.

Pump

Boros can go either wide or tall, but it's all aggro. Tori D'Avenant, Fury Rider and Heroic Charge encourage going wide with goblin and soldier tokens, but Valduk, Keeper of the Flame, Kemba, Kha Regent, and Danitha Capashen, Paragon prefer an equipment suite. Either way, cards like Baird, Argivian Recruiter and Heartfire Immolator that care about power get a boost.

Pendelhaven

This one was arguably conjured out of thin air, since the key cards are Pendelhaven and Sigil Captain, but there are so many soldier and saproling tokens that it requires no real support. The deck wants to stay 2-color, unlike most green decks, because the white pips are so demanding.

Spells

DOM Izzet leans aggressive while DMU cards lean interactive. Burst Lightning and both goblin and wizard tribal support help the more aggressive version. Kicker cards play nicely in a long game, though, and the card quality makes Roost of Drakes fine as the only kicker payoff.

Saprolings

This deck is my favorite. Saproling cards naturally work very well with Domain, so they can span the gradient from 2 to 5 colors. The Golgari version leans towards Slimefoot and Golgari Germination, while the 5-color version leans more heavily on Undercellar Myconid and Domain.

Goblins

The fun police are here to make sure everything's not 5-color soup. Goblins had a weird amount of support for a nonexistent cardpool in DOM, so I've tried to fix that. In Gruul, Kicker additions help beef up Bloodstone Goblin, which didn't get there in DOM but has better support with the DMU card pool. Izzet has good Kicker spells, and Balmor, Battlemage Captain loves Hordeling Outburst. Boros and Rakdos love the expendable bodies for cards like Heroic Charge and Garna, Bloodfist of Keld.

Yargle

"Gnshhagghkkapphribbit."