Do you know how much space windows normally takes up as my SSD is only 124GB, and I would like a little space for a couple of games.
As nondy said, you'll be fine.
Just make sure you disable hibernation (it takes 6-7GB of space on system drive) if you don't plan on using it by running command prompt as admin and typing the following:
powercfg /h off
Also, if you have 8GB of RAM or more you can reduce the size of pagefile to 1GB (it usually is the same size as your total RAM - big waste of space) since, in that case, it's never used by anything other than Windows itself.
You can do that by clicking 'Advanced system settings' in System (Computer) properties window, then clicking on the first settings button (within performance section), then switch to advanced, click change, untick 'automatically manage paging file', selecting C:, custom size and finally type in 1024 and click 'Set'. Confirm it by clicking OK in every box you opened to get there, if done right, you'll get prompted to restart the PC which you should do for changes to take effect.