A Space Shooter For Two Bucks! Easy space bucks
Play Helyix and Blattar VI first, then get the Remnant Vacuum for 50,000 space bucks. When you play Survival mode, the space bucks will be attracted to your shop, and you will be able to gain them quicker.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art / Original