Unlike the past, RAM speed and timings have a marginal impact on real performance. Our pick falls on DDR4-3200 models, with the exception if price difference with DDR4-3600 is close to minimal. Intel's Alder Lake platform supports DDR5 memory, but it doesn't currently offer any significant performance gains over its DDR4 counterpart. AM5 platform from AMD supports DDR5 only.
Dual channel further improves performance, so using two modules instead of one is the best choice. If you are looking to upgrade in the future, it is recommended to buy just one module. Otherwise, a memory kit consisting of multiple modules remains the best choice.
The recommended minimum RAM quantity is currently 8 GB for low-end systems. Some video games or applications might be more RAM intensive, so 16 GB is the recommended value for most systems. Any higher value might be really expensive and not necessary unless it is required for specific applications that demand a lot of memory, but it can still be a good investment. There are no recommended brands or models, just make sure the above criteria matches to what you are actually looking for (quantity, speed, and voltage).