For the bearings, use grease. Oiler systems are out of the scope of what you need. These days the only machines using oil mists are large spindles running very fast (40krpm HSK50 for example). The bearings you buy will actually tell you what to use for a given preload and rpm. If you are using cheap bearings, none of this will even matter.
I was at CMTS today and saw a number of rather nice spindles.
you should look at:
Meyrat
NSK America
Jianken
Microlab
Andersen
HSD
Those guys all make small spindles, some with motors, some belt, some direct, ranging from hundreds to tens of thousands of dollars. Microlab basically makes exactly what you are trying to do, for about a grand. Study how they have laid them out, power, bearing size, rpm limits.