Ah you got that one 😀 I was looking at it since I've got a banshee with broken memory from the same seller, was considering it for parts.
That actually looks pretty good in my opinion, all the pads are still present and the areas that will contact the AGP slot pins (wider part) are still mostly intact. Check that none of those pads are shorting adjacent ones.
Take care from here because cleaning too hard and detaching a pad will make it much harder to get it working. What I'd do from there is carefully scrape back solder mask where the pad goes into the trace - only where those appear black though. You could take an even more cautious approach and not do that, but scrape a little solder mask off further up the trace on the main PCB (not the edge) where it's uncorroded / undamaged, then measure resistance between there and the pad to see which ones are damaged. It could be that the solder mask has gone black but the trace is still okay.
Or you could just test it, now you've cleaned the pads up enough that it looks like they won't short with each other and you could use a full test to determine whether 100% of the needed signals are there or not.
For long term storage/use though, I do recommend cleaning off blackened solder mask and putting some fresh solder on that trace with flux. Put Kaptop/polyimide tape over the edge connector pads area to mask them off when doing that though, getting solder onto the gold pads area is impossible to clean off fully.