What are some examples of "quick wins" you should aim for in the first 90 days?

Regarding quick wins in the first 90 days, I think you need to be mindful of what you are trying to deliver. If you come in and start building and delivering to “stop the bleeding” of top priority issues without understanding the business you might end up creating more of a mess in the future (forest and trees).

Instead focus on the first 90 days, really understanding the business, how it operates, what the goals are, what is working well, what is not, etc. and building a realistic plan for delivery in the first 30/60 days and starting to deliver on that plan. The foundational items are going to be key, ensuring have lifecycle, clear KPI definitions, data infrastructure, standard operating procedures, seller processes, etc. are always P1s.

If you are eager for quick wins, look at key business as usual processes that occur on a repeat cadence and tend to be manual and look at how to operationalize those. Anywhere that administrative time can be decreased for items that are stable and repeatable opens up additional bandwidth and are good quick wins for scale.