How I should pay tax if I buy Bitcoin from an overseas friend
The $1 is a Capital Gain (it's not income except perhaps if you're a professional trader). So, if there's tax to be paid, it will be Capital Gains Tax, not Income Tax. When you declare your total Capital Gains and your total Capital Losses to your tax authority, they will tax you on any net gain over and above your personal allowance (which will depend on your personal circumstances). See https://www.irs.gov/taxtopics/tc409.html