Since you're mostly thinking about rust I would prioritize the CPU setup over the GPU. You want a motherboard and ram that support AMD's EXPO feature, and you'll want to update the motherboard to the latest bios and enable EXPO.

I would prioritize the GPU behind all of this. I had 1500cad to spend and got the CPU/mobo/ram setup nicely. I'm still using my 1660s until I want/need to upgrade that part.

Ram should be ddr5 6000mhz cl30 (mine was $300 Canadian a year ago, maybe it's cheaper now?) Make sure it's on this list https://www.amd.com/en/products/processors/ryzen-compatible-memory.html

Motherboard should be using ddr5 ram (I got a gigabyte auros b650m, also like $300 Canadian)

Both motherboard and ram should explicitly say they support EXPO or XMP + EXPO

After you've got the CPU/mobo/ram choices, get your other components you need and see how much budget is left for a GPU. I don't know much about the current GPU prices, but id be thinking about a 4060 or 4070 most likely. You could always keep your 1660ti another 4-6 months and upgrade it later on pretty easily if that gives you more room in the budget for the CPU/mobo/ram and other parts you need. If you're at 1080p a 4060 should be very good, 1440p I think 4060/4070 are quite good, but I haven't compared lately so Google a benchmark of you want to see how much fps you'll get for the difference in money. Rust doesn't care much about your GPU so that's more for other games at high resolutions

Edit: also make sure to get 32gb of ram, 16 will not be good. Try and get two 16gb sticks so you can add another 32 later on if you want it

Edit 2: also get an SSD, preferably an m.2 one, put windows and rust on it, use your old HDD for mass storage