I'd rather over-purchase on ram and never have to think about it again rather than try to carefully tailor the amount of memory in the machine based on the workloads I think I'll be running on it at the time of purchase. Fortunately my latest server upgrade was before the ram prices went insane.
I generally run “obsolete” machines and then just max them out on RAM and CPUs, stick a dual 10G card in the 16X slot, and shove the latest NVMe SSDs in the 4X slot and forget about it.
For bulk storage / logs I toss in a few of whatever the cheapest drives are right now.
Have lots of spares for failures… haven’t had one failure since 2019.