51 cards where the color identity ≤ GU and the text includes “proliferate” and the USD price < 5

Adaptive Sporesinger (Phyrexia: All Will Be One #157)
Bloated Contaminator (Phyrexia: All Will Be One #159)
Bloom Hulk (War of the Spark #154)
Cankerbloom (Phyrexia: All Will Be One #161)
Carnival Elephant Meteor (Unfinity Sticker Sheets #7)
Carnivorous Canopy (Phyrexia: All Will Be One #162)
Contagion Clasp (Scars of Mirrodin #144)
Contagion Engine (Breaking News #61)
Contagious Vorrac (Phyrexia: All Will Be One #164)
Contaminant Grafter (Phyrexia: All Will Be One Commander #17)
Contentious Plan (War of the Spark #46)
Copper Longlegs (Phyrexia: All Will Be One #165)
Core Prowler (Mirrodin Besieged #103)
Courage in Crisis (Commander Masters #278)
Everythingamajig (Unstable #147a)
Evolution Sage (The Lost Caverns of Ixalan Commander #240)
Expand the Sphere (Phyrexia: All Will Be One #168)
Experimental Augury (Phyrexia: All Will Be One #49)
Ezuri, Stalker of Spheres (Phyrexia: All Will Be One #201)
Flux Channeler (Commander Masters #847)
Fuel for the Cause (Mirrodin Besieged #25)
Gitaxian Anatomist (Phyrexia: All Will Be One #52)
Glistening Sphere (Phyrexia: All Will Be One Commander #20)
Guildpact Informant (War of the Spark #271)
Inexorable Tide (Fallout #177)
Karn's Bastion (The Lost Caverns of Ixalan Commander #339)
Kiora's Dambreaker (Ravnica Remastered #48)
Merfolk Skydiver (The Lost Caverns of Ixalan Commander #277)
Mesmerizing Dose (Phyrexia: All Will Be One #62)
Mutational Advantage (Fallout #111)
Park Heights Maverick (New Capenna Commander #63)
Plaguemaw Beast (Mirrodin Besieged #87)
Planewide Celebration (War of the Spark #172)
Pollenbright Druid (Commander Masters #312)
Recon Craft Theta (Fallout #141)
Reject Imperfection (Phyrexia: All Will Be One #67)
Roalesk, Apex Hybrid (New Capenna Commander #349)
Serum Snare (Phyrexia: All Will Be One #68)
Smell Fear (Modern Horizons 2 #173)
Steady Progress (Modern Masters 2015 #58)
Tainted Observer (Phyrexia: All Will Be One #217)
Tezzeret's Gambit (Outlaws of Thunder Junction Commander #117)
Thirsting Roots (Phyrexia: All Will Be One #185)
Throne of Geth (Double Masters #301)
Thrummingbird (Commander Masters #858)
Unnatural Restoration (Phyrexia: All Will Be One #191)
Urban Daggertooth (Modern Horizons 2 #181)
Venomous Brutalizer (Phyrexia: All Will Be One #193)
Vexing Radgull (Fallout #41)
Viral Drake (New Phyrexia #49)
Vivisurgeon's Insight (Phyrexia: All Will Be One #77)

The arc of my blade has carved a path of light to the end of these results.