Corns, kings, and milks come in all colors of the sun, and can all be found for even under $50.

Other species to look at are kenyan sand boas, childrens pythons, western hognose snakes

Of the ones that make easy-peasy pets husbandry-wise and with good temperments, the above are all good choices. People may chime in with other ideas too.

There are other snakes that are small, but don't make my "top smaller pet snakes" list for various reasons.

Personally I suggest a corn, hard to go wrong with a corn snake