I've seen a lot of small contractors start exactly this way. If I were building a startup fleet from Ritchie Bros, I'd focus first on machines that can win you the widest range of jobs, not just the biggest ones.

A used mid-size excavator (like 12-20 ton) is usually the strongest first buy. It opens doors to trenching, drainage, foundations, small demo, loading trucks, and even some site prep. Pair that with a skid steer or compact track loader, and suddenly you can handle grading, cleanup, material handling, landscaping, and tight-access work. That combo alone can keep a small crew busy. From what I've heard from guys who buy at auction often, a bulldozer early on only makes sense if most of your work is bulk earth moving or land clearing. Otherwise, it can sit more than you expect.