New rig
I stupidly forgot my password to an old wallet and now need to build a rig to deal with my problem. I built a mining rig back in the day so I have an idea what to do but I don't know what the best components would be for this specific application. Any suggestion would be welcomed thanks.

If you know enought of your password, a laptop can be enougth. Buying a GPU this year is really a bad idea.

I followed the informations on this page this time.
As CPU I chose the 5600X Ryzen. But you can even save more. Depends if you deal with large lists and pcfg cracker, you will need more than 32gb of ram. Large lists = multiple milliards of lines.

Maybe one here can help you if you can narrow down your lost pass enought. As you deliver your hash only, noone can steal your funds if your are not hacked :-)
Yeah I thought I did know enough of my password and have been putting my pc to work running a list I made but still no dice, it's an older pc but it seems to put up good numbers. It's unfortunate gpus are so sparse.

I will look into that link you provided thank you. I can find motherboards and cpus but gpus nope. Does it matter what brand of ram?

That would be very helpful and I didn't really think of that. Lot's of good info here!
Yeah I like the page. No, the ram brand does not matter as your are not up the last edge. The size matters :-)

If you do not plan to make lists with multiple billion lines, you should be fine with 16gb. But if you find a good 32gb you want to take it. Spend the most on the GPU.

I have 2 2080ti which I could offer you. But not for weeks :-) tha's why I asked if you know more about the password in order to decrease the time. Is it the BTC or an electrum wallet? The electrum attack is pretty fast.
I think I will go with 32gb of ram since its not too expensive. Its a litecoin wallet :\
Are the amount of cores the most important factor for gpus running hashcat?
Yes. You want as many as possible. Check out for hashcat benchmarks with specific GPU's. I think mostly it is Nvidia ahead of AMD. But you also want to consider speed vs cost...