I wouldn't worry to much about RAM use, as Seven will free up RAM on its own when needed.
It will use as much as it can to make things faster. Around 750MB-1GB of RAM should be normal at idle. Nothing to worry about here.
4GB would be the sweet spot for 7, but 2GB should be suffecient. Especially for Internet Games etc. Will only be a issue with grpahic intensive games or any other memory intensive tasks.
I wouldnt try to tweak it into using less RAM however, aside from disabling un-needed start up programs.
One other thing to consider aside from the link Petey7 provided, what Antivirus are you running?
I would start with cleaning up junk:
Run CCleaner,found here : CCleaner - Optimization and Cleaning - Free Download
and a quick scan with Malwarebytes, found here: Malwarebytes
Youd be surprised how much junk files CCleaner will remove, and much it can help.
Alternatively, open a elevated CMD promp (in start search box type cmd and right click the result and choose run as admin)
Click all the little boxes (except maybe thumbs if you do not want to regenerate them after)
then type: cleanmgr sagerun:50
this will clean up all other temporary files and junk files that are no longer needed.