on the bottom rung (of the ladder)

1. Occupying the most basic or fundamental position in a given group. Quarks are on the bottom rung of the ladder when it comes to matter's physical makeup. We'll need to start getting supplies ready. On the bottom rung are the standard things—pens, paper, folders, that sort of thing.

2. Occupying the lowest position in a hierarchy, as in terms of power, influence, respect, etc. Tech startups may start on the bottom rung economically, but, given their business model, they have a very high potential for growth. Warehouse workers are on the bottom rung of the ladder, so we're often not treated with as much respect as those working desk jobs.