Hello, The linux OS is different from windows, It uses almost all RAM all the time and its normal, it installs a cache engine in RAM so it shows RAM used, You can see your swap is not used, and this is the way linux is organised.
Even if you see swap it does not necessarily mean that your system has used up all your memory. Linux may decide to push rarely used processes' memory to swap leaving you with more free RAM for your other processes.
Both are good. The more buffers and cached stuff you got, the better your system will run. When using the 'free' command, the line that says "-/+ buffers/cache" is a good estimation on how much memory your system is using without the buffers and cache taken into account.