I have never actually played the archetype, but I can think of a few upgrades off the top of my head that won't break the bank:
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Kiora, the Crashing Wave : gives you a little more of everything you want in this deck by blanking a bit of damage, digging for combo pieces, and can start spitting out 9/9s.
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Ricochet Trap : With two or three copies in the board it will help you fight through counterspells, by switching their target to the trap itself.
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Lingering Souls : In the board it gives you more chump blockers, pressure on opposing combo/control decks, and sac outlets for
Greater Gargadon.
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Wear // Tear : Hits pesky targets that don't die to
Restore Balance.
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Blood Moon : Not truly "budget", but it is much cheaper with the MM17 reprint, and I would take advantage of it while it's still low.