Build a Changeling army to access various tribal effects and wipe boards while attacking with Silumgar, the Drifting Death on board.

A few words on some cards:
Mercurial Transformation: Destroys ANY nonland permanent. You can destroy an artifact or enchantment, cards that UB struggles to deal with.
Synchronized Eviction: Costing 3 mana somehow works as a short term Chaos Warp who doesn't give something back.
Mass Diminish, Polymorphist's Jest and Sudden Spoiling: Allow you to easily wipe the board with Silumgar's passive ability.
Glimpse the Cosmos: Pseudo Ponder 2 times for 3 mana.
Liliana's Contract: Solid card draw and offers an alternate wincon not that hard to set up (note that Hidetsugu and Kairi is a demon!).
Rush of Knowledge: Very underused EDH card. Draw 6 for 5 mana with your commander on board.
Coveted Prize: I make a point of never playing tutors in EDH but this budget decklist lacks redundant expensive cards so this very powerful tutor makes up for it. Tutor anything for 1 mana and pseudo ramp for 4, yes sir.
Absorb Identity: 2 mana instant speed bounce isn't bad but it can also win the game by transforming all your shapeshifters (changelings) into a powerful creature.
Peer Pressure: Can steal entire boards.
Reflections of Littjara: Say "dragon". You can also say "Shapeshifter" depending on what you have in hand. Card types break down in "Cards data" below.
Psionic Ritual: Do I need to say changelings are horrors ? It's powerful at finding solutions to your problems and overall a very serious alternate wincon.
About the decks' creatures, clones are here to act as changeling slots since there aren't enough to reach the needed critical mass. Play the changelings first and copy them. What's important here is the low mana cost of the creatures. The deck would play 24 one mana changelings if it could.

The most powerful upgrades available are the non-legendary clones and Necroduality.
Link to the non-budget decklist I'm playing

> Cards data:

Changelings: 13 (11 + 2 tutors)
Nightscape Familiar: 35 reductable spells (+ Silumgar)
Reflections of littjara: say "Shapeshifter" or "Dragon".
-Shapeshifters : 16 (11 changelings +2 tutors + 3 clones)
-Dragons: 18 (11 changelings +2 tutors + 5 Dragons)
-("2 tutors" are Cateran Summons and Step Through)
Bloodline Pretender: Say "Dragon"

> Taplands: 10

Contaminated Aquifer
Creeping Tar Pit
Dimir Aqueduct
Dismal Backwater
Ice Tunnel
Mistvault Bridge
Myriad Landscape
Path of Ancestry
Sunken Hollow
Temple of Deceit