I think you miss my point... or maybe I missed yours.
If you're familiar with Excel, then you have some understanding of spreadsheets.
At its heart, Numbers is a spreadsheet application, just like Excel, and there is a direct correlation between the two when it comes to the basics (rows, columns, references, formulas, etc.) to the point where most things just work the same way. Even the formula syntax is identical. So it isn't clear what part of Numbers you're struggling with.
The most significant difference is that Excel uses a monolithic approach (each Excel sheet contains millions of cells (≈1m rows x 16,384 columns)), whereas Numbers adds one level of indirection in that a sheet contains one or more tables, where each table has its own set of rows and columns, and can grow independently:
Excel: Document -> Sheet(s)
Numbers: Document -> Sheet(s) -> Table(s)
For small setups (e.g. a single table per sheet), the difference is transparent to the point of irrelevance, but for larger setups the table separation can make for easier handling.
(Note: Excel does have a concept of 'Tables' for laying out tabulated data, but it's still integrated into the main grid on the sheet, not a distinct space as in Numbers).
I will say that Excel does have way more 'bells and whistles' that don't always have a direct equivalence in Numbers, but that's why I said that the learning curve depends a lot on what you're trying to do. If you're a power user and are looking for an equivalent to Excel's macros or VBA scripting, then you're out of luck since these aren't supported in Numbers. Likewise with Excel's array-based functions, which Numbers doesn't support.
When it comes to charting I find both Excel and Numbers equally frustrating... easy to get a basic chart, but both require a lot of tweaking to get the visual I'm looking for. Excel probably has the edge with a few additional chart types/features, but again it depends on what you're aiming for.
So, like I said before, the basics are very similar. Excel has some additional features/functions. Numbers is generally seen as easier to use. If you want to share specific 'how do I...?' questions I think you'll find lots of people here willing to step in and help out, but there isn't a one-size-fits-all answer to that question.