How much should I be saving per month?

I am a 20yr old living in an apartment with my partner. After taxes I make about $1400/month and was wondering how much I should be saving at this point in my life. I have calculated my monthly expenses (keeping in mind entertainment/and miscellaneous purchase) to be about $900. If it helps, please see my exact budget below: Rent: $300 Cable/Internet: $75 Cellphone: $30 Auto Gas: $80 Car Insurance $60 Car Payment: $100 Groceries: $100 Health/Dental Insurance: $80 Etc: $100
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I have always tried to save a minimum of 10%. 15% or 20% is best, but not always possible. How do you spend $100 a month on food? You eat three meals a day for less than $4 a day?!?!?!?!
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