On 8GB RAM I have ~2GB occupied (25%). It totally depends on no. of programs/software installed on your PC and no. of background services.
avgcsrva.exe is "AVG Scanning Core Module - Server Part". It runs scans on your PC in the background and is definitely a heavy process. I suggest you to uninstall AVG and use a lighter AntiVirus software such as Avast! AntiVirus.
I tried view memory by the program : RamMap. But it's not working on Windows 10 TH2 (Working on TH1). I got the error - "Error refreshing database".
I found out that "System and Compressed Memory" process take 35MB (highest memory). Which Antivirus/Internet Security do you use ?
If you have a 4GB RAM and in use is 30%, then it is a 1.2 GB. What do you want? It is less usage if at all possible. This pc must be empty, only Windows runs.
Well, with 4Gb and antivirus running, browser not open, I have around 900Mb used in memory. This on W7, so how exactly BOTH W8 and W10 claimed to lower memory usage?
% of RAM used is not important, as it will differ depending on how much RAM you have installed RAM usage is what you want to look at, in MBs/GBs