That depends entirely on the price; things are very different when it costs $20k/kg to orbit (basically nothing is worth that) vs. $20/kg to orbit.

Some people are suggesting making high quality fibre optics and pharmaceuticals in LEO already with Falcon prices:

https://en.wikipedia.org/wiki/Space_Forge

https://en.wikipedia.org/wiki/Varda_Space_Industries

While I am *extremely* skeptical, I've heard people talk about space-based solar. I mention this only so nobody adds an "and also" for that.

Ditto anyone talking about lunar He-3. This is a bad idea, "why" is long enough to be worthy of a blog post.

But if you were committed to expansionism for whatever reason, then you'd want some way to get industrial quantities of steel from mines already in space, to make the factories themselves cheaper. Possibly megastructures like an orbital ring, too.