Finding out where to start

[citra]

background:
I have been machining with haas cnc lathe for over a year with the gcode program I made from a template. The program is using rpm, feedrate, etc... which were recommended by the sales people.

present:
I am trying to cut down on cycle time and also to increase quality. A friend told me that before I try to experiment with it make sure what I'm using are correct in the first place. What I want to find out is if all the rpm, sfm and other numbers I am using are correct. But how would I do it?

I am machining mainly 14k gold tubes with diamond tipped inserts. Am I supposed to look at the hardness of the tube and figure out the speed/rates? or am I supposed to look at the inserts that I using first? I am kind of lost here and any help will be appreciated. Thank you.