Which Machop to evolve?

None, but if i had to chose: nr 1

1st one. Easier to go for breakpoints.

If candies aren't rare for you #1 is good.
Otherwise you'll probably want to invest candies in one which already has DP.

Yeah, easily the first one. Its ready to battle how it is and has a perfect attack IV. None of them is worth to invest dust into anyway.