Should I add another 16GB of DDR5 now or wait for a better price?

If 16GB is limiting what you do and the upgrade fits your budget, buy it now. You get the extra capacity and a second memory channel instead of waiting for a sale that may or may not happen.

Just don't buy out of panic. RAM prices can move either way, and nobody can reliably tell you when a good deal will appear.

I'd check memory usage during your usual games and other demanding tasks first. If things are running smoothly and you aren't close to filling 16GB, waiting is a reasonable choice. Set a price you're comfortable paying and keep an eye out rather than betting on a particular sale.

For a second stick, look for the same model and specifications as your current one. Two separately purchased sticks can still differ internally, so matching the model improves your chances but doesn't guarantee they'll run together at their advertised settings.

If you can return the single stick for a full refund, compare that cost with a matched 2 x 16GB kit. A kit is tested together and is the cleaner option if the price difference makes sense. Check your motherboard's memory guidance and recommended slots too.

Think about what you'll use the PC for over the next year. More demanding modeling or rendering work could make the extra capacity useful, even if your current games are fine. If that's only a possibility for now, there's no need to pay a premium just in case.