Speed and feed are both very wiggly concepts regardless of available equipment, do what works for you and your machine with the material you are milling/turning. Size matters a good deal, turning a part on a lathe that is 1" out of the spindle is considerably different then a part that is held in a steady rest 20" out.
I have the luxury of using my employers tools, I do however have time constraints for each job. I begin at what I think the tooling/part can handle from past expeirence and run it hard, if I get a poor finish or rapid tool failure then I begin to slow it down. When I owned my own shop (20 years) I worked in the opposite direction, start slow and then get faster.
To sum up, there are untold numbers of speed and feed charts/formulas/misinformation/old wives tales/outright BS, do what works on your machine, over time you will know what will work and what will not work. At this point you will have become "a machinist" (-: