Cheap Crystron

The 25 Crystron main deck cards + sample Extra Deck together are ~$30 USD on TCGPlayer (Jan 2025), and 13/15 of the non-engine assume you bought the Blue-Eyes White Destiny structure deck x3. Otherwise, just toss in your old shredded copies of Dark Hole or whatever until you hit 40 cards.

The lack of Quariongandrax is covered by Satellite Warrior and Vimana. Accel Synchron's there to make Satellite Warrior easier to summon, and Rion's similarly there to 3 + 7 (your synchros) for Satellite, or you can just normal Ash Blossom + 7. If you need more space in the extra deck for whatever secondary engine, you can cut 1x Dawn Dragster, Accel Synchron and Mechaba.

Otherwise, it plays 95% the same as full power Crystron, except you lack the Citree + Tistaros endboard if you're uninterrupted, and Satellite Warrior isn't as good as Quariongandrax and has a high chance of getting locked out on your turn before you have the material (Sulfador's machine-only lockout).