However for most home machinists, an inexpensive coolant pump will provide much more satisfaction, over time, than a drip oiler. Of course you will have to come up with a coolant recovery mechanism to recycle the coolant but that is a minor issue.
More to the point is that you will have a better choice of coolants that you can more readily change to suit the work which will result in a better surface finish. There are many different water soluble coolants for ferrous and non-ferrous stock that can keep the cost in check.
A fog or a flood of coolant removes more heat from the working edge of the cutter than does a drip. Size your coolant delivery orifice to the needs of the work.
Freeing up both hands to control the work is priceless.
A better surface finish at the machining phase saves hours of polishing later.