You want it to be equitable, then you should do this...
3% tax on food and other consumer staples
6% tax on cars under 20k, houses under 300k, consumer products (dishwashers, fridge, etc)
10% tax on non-essential goods (60inch led tvs)
40% tax on luxury items (your diamonds, 60k mercedes, 1 mil homes)
And yes, I'm all for abolishing the IRS, but a flat tax is anything but fair.