For the storage you have an additional option: converting a PCIe slot to M.2 Nvme is possible with a passive addin card. This way you could keep the current OS drive and add a 2TB m.2 instead of a SATA one. Since M.2s are quite cheap I went this route last year. Just be warned that secondary x16 slots are slower: it looks like 2.0 x4 for the b450-a pro max.
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.
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.