How much ram can Lenovo H500s handle?

I'm looking for a gaming alternative to a casual pc, i want to maximize the amount of ram possible and i would also find it helpful if you could suggest any ways to make it better i.e graphics card etc. If you know the best possible graphics card it could use that would also be helpful. Thanks in advance.

Added (1). http://www.very.co.uk/lenovo-h500s-intelreg-pentiumreg-processor-8gb-ram-1tb-hard-drive-wifi-desktop-base-unit-black/1409526616.prd?aff=google&affsrc=acquisition&cm_mmc=google-_-PLA%20-%20Generic-_-All%20Google%20PLA-_-452_18283950120

If you go to the crucial memory site and run the memory scanner it will tell you what yo have what the max is and what your upgrade options are. In general though more than 8GB is unnecessary.
Here is your link
http://uk.crucial.com/gbr/en/systemscanner?cm_mmc=google-_-uk-_-brand-_-null&ef_id=UeoGwwAABXoyg@kj:20140723030434:s
HTH
David