Watch a few XLookup videos on youtube you'll blow their minds

If you're not going to use Excel all that much, the sum() function.
If you are going to use it a lot, pivot table filter.
If you're a visual learner, conditional formatting.

If you need to know how to do something with Excel, you can just look it up. It's so widely used and universal there's tons of sites dedicated to doing stuff it in. Most jobs you don't even need to do anything fancy for either. Like Pivot Tables? you'll probably never used them, but if you do, they're literally a button under the data tab. Edit: it's actually in the Insert tab not the Data tab.

The actual best "trick" I've learned is that you can hit Ctrl+Shift+ an arrow key to quickly select multiple cells.

Microsoft's Excel Quick Start guide (will download a PDF): https://download.microsoft.com/download/5/3/0/5303FC2D-E52C-41F9-A4E3-EC99D7D7019D/Excel%20QS.pdf

Cheat sheet with common tasks and keyboard shortcuts: https://www.customguide.com/cheat-sheet/excel-cheat-sheet.pdf

General tutorial with chapters https://www.excel-easy.com/

Biggest piece of advice I can give you: Excel is about learn by doing, not about knowing the program in and out

1. Pay attention to what your job asks you to do in real, practical terms
2. Hack together a way to do it on Excel until you have some grasp of it no matter how inefficient it feels at first
3. Refine, refine, refine. Keep looking for ways to do whatever tasks or functions you use the most, but faster, until you get the general sense of "yeah I get it". Don't even slightly worry about anything you don't immediately need
4. When in doubt, look it up. I've been using Excel since 1998, I now swap between it, Google Sheets, and the OpenOffice equivalents depending on what I'm up to, and I still need to look shit up a lot. There is no shame.

Learn to look up functions, don’t memorize them. When you start typing a function out (by typing “=“) it will give you a pretty decent top level prompt for what each part of the function does, separated by commas. But you will be far better off just looking them up as you need them than anticipating what your job needs. For instance, I’ve used IFERROR, VLOOKUP, SUM, SUMIF, ROUND and others nearly every day, and a friend who also uses excel every day blew my mind with CONCATENATE, a function I would have never needed in my job, ever. It’s a bonkers expansive program, and you’re only ever gonna need like 5% of what it can do. I also used Pivot Tables a lot, which so many interviews asked about. But always, always look it up. It takes two seconds and there’s absolutely someone else on some 2007 forum post who had the exact same problem. Good luck!