>>33255714 (OP)As much as you can.
I personally set a investment goal first and then work out my expenses after that. For example if you make $1800 after taxs each week then you could save $1000 and work out if you could live happily on less then $800. What ever you have left of that $800 when you get your next pay check you can then choose to splurge on something you want or also invest.