Boss DS-1.
It was voted one of the all time best pedals to have.
It works super with the Monkey. Put the DS-1 first that way when it's on and you hit the Monkey it allows you to really shape the sound of the DS-1 output. The Monkey has much better tone control and will smooth out the buzz of the DS-1.

I love mine in that combination and have used it for all my gigging for the last 12 years.

Used delivered on fleabay around $30 or less. That leaves $60 or so to spend on milkshakes.