Should I get 16GB RAM now when building my new PC?

It's definitely a reasonable plan given current prices, but I'd suggest going for 2x8GB right from the start. This will help you avoid using just one RAM channel, which can hurt your performance.

I wouldn’t recommend getting a single 16GB stick. It’s better to get 2x8GB if you're sticking with 16GB, as mixing RAM can cause issues. Plus, having two sticks will allow you to utilize dual-channel mode, which is faster. Most motherboards have four RAM slots, so you can always add another 2x8GB kit later to reach 32GB if needed.

If you're set on 16GB now, just make sure you buy from a reliable brand so you can get a matching kit later. Mixing RAM can lead to problems, so try to stick with the same manufacturer and timings.

You might want to look up the differences between dual-channel and single-channel RAM. It's essential for performance. Also, keep an eye on deals—I've found decent RAM for much cheaper on local marketplaces, so it's worth checking out.