What percentage of income should go to savings?

As a student in newyork, saving plays a huge part in order to cutoff for the things that I personally like to buy. Knowing the fact that there is a family who is supporting me, but still as a university student there is a planning that we need to do as well.

I can explain the expenses and wants and savings in percentage below:
50 % is the Needs _ food, transportation, study supplies, minimal rent
30 % are my wants like Guitar strings, Sneakers, new jacket, New books etc so these are the things that are depreciable overtime and requires investment.
remaining 10 – 20 % are the expenses for the savings that are a must.