The first upgrade is easier to choose after you name the part of the loop that keeps costing money. If vehicle loading, selling, or shop space slows down, every auction after it becomes less profitable.
Vehicle space comes first when good items are being left behind. If you win a locker and cannot carry the best pieces, the missing items are lost profit. More carry capacity or a carry-related improvement can pay off because it lets the same winning bid return more value. This is most noticeable when lockers contain strong base-value items, profit-raising mutations, or several medium-value objects that would otherwise be left on the floor.
Shop or selling improvements come first when items pile up after the trip. If the vehicle returns full but cash comes back slowly, the shop side is the bottleneck. Selling space, inventory space, or faster clearing becomes more important than chasing another auction. Cash trapped in unsold items cannot protect you from a bad bid, pay for the next locker, or help you test a new area.
Bidding discipline comes before convenience. A player who overbids every locker will not fix the problem with more space. If the final auction price is too high, the upgrade only helps you haul more weak margin back to the shop. Bid ceilings and skipped overpriced lockers make the later upgrades return more value.
Robux purchases need a named bottleneck. Car weight, inventory space, selling space, and quick selling effects can solve real bottlenecks, but they are not automatic profit. They make sense when they fix a repeated problem you can name. If most losses come from chasing bids too high, better auction decisions come before Robux.
Early upgrades should change the auction loop. Cosmetic choices, collection goals, and comfort purchases can wait until your cash flow is stable. Early progression is strongest when each upgrade either lets you carry more valuable loot, sell faster, or keep enough cash on hand to survive a bad locker. Once those pieces are stable, later purchases become safer because the business can support them.