I disagree with the idea of upgrading RAM. 16GB will be fine for at least a few more years.
Add an additional SSD. 500GB in almost 2024 is unusable except for editing txt files.
Maybe get a second monitor if you don't have one. 1080p 120Hz TN should be pretty cheap.
Update the CPU to anything X3D. There's some relatively cheap X3D options now.
I've looked at CPUs but my motherboard wouldn't support X3D.
Even with a BIOS update?
Not all m.2 SSDs are created equal. I would look at what the fastest SSD your motherboard supports is and look at that for an upgrade.
I believe an others have said a nice 1 or 2tb SSD that is PCI based should help out. Picking up an additional 16GB of ram isn’t necessary but neither is any of this and would likely let your system last even longer. There’s also a good chance your b450 motherboard supports newer x3d variants of the 5000 series ryzen CPUs through a BIOS upgrade. If you have a microcenter you can try to snag one of the 5600x3d processors or snag a used 5800x3d or maybe one on sale.
What’s your ram situation?
This is what I have VENGEANCE® LPX 16GB (2 x 8GB) DDR4 DRAM 3200MHz
Adding 16 GB to that should be cheap if you have four slots. I would recommend doing that along with an upgrade to a 2 TB m2 ssd. You can just clone your old drive to your new drive using clonezilla to fix the partition size.
I did exactly this upgrade a few months ago. I did it so I could stop worrying about running out of storage. Don't expect much performance improvement from the ram and ssd upgrade, though.
For a significant performance upgrade you can get a ryzen 5 5800 or 5800 x3d for a little more. That's the cpu I went with and I've been very happy with it.
Make those upgrades first, then decide if you want to look at upgrading the graphics card. What you have should keep up just fine for now, though, assuming you're not trying to max out unoptomized games.
Do whichever one or 2 you can afford but upgrade to a 5700x, add an SSD, and 32GB for extra breathing room for Windows