16GB of RAM is enough for most apps and gaming. You can check your memory usage in Windows using Task Manager whenever you feel an app or service is hogging the system. Look at background services under the Processes tab and under the services tab. You can then go to your Local Services and modify those services to disable, delay or stop.
For Services, hit windows key +R and in the box type "Services.msc". When modifying Services, be careful not to disable essential Services and if not sure, Google it. Microsoft update service is one that you can stop or disable that can hog your system.
Increasing your page file quota can also help if memory is running low.
Other things can hog memory. Viruses or Malware, so run Malwarebytes or your Virus checker.
DIMM stands for Dual in-line memory module. Your Ripjaws are a good set.
List your MB and I can tell you what your options are if you want to install more.