How much student discount can I get?

I don't see a stated % (I believe it may be 10%) but to browse with educational pricing go to Education Pricing and Student Discounts - Education - Apple

If the USA is not your country, go to the bottom right where you see it say "United States" and select your country from there.

I believe you may need to browse the Education Store and compare the prices on individual items / configurations to prices of the same Items / configurations in the regular online Apple Store.