It looks like your system is maxed out at 16 GB of RAM.
Check this out to see if it is your model
SSD storage is a great idea! But, can be quite pricey depending on the size you are looking for. I might suggest, de-cluttering your drive and making a TimeMachiene backup of it.
If you don't have any important software/still have the installation/purchase licenses for it, I might even suggest doing a fresh install and selectively copying items from your TimeMachiene back onto your system.
At the moment, I have a 13" MacBook Mid 2010 that has 3 GB of RAM in it. I don't use it for anything too heavy, but it has a fresh install of Sierra on it and it is flying fast. So that is my experience with fresh installs.
Good luck and let us know what you end up doing!