Well I'm starting a Legion playthrough for the first time and I was wondering how you did things. I have already given Good springs to the powder gangers and I am intent on being evil. However I am curious on how you did things?

You can play rather normally. Just don't do anything important for NCR. Powder Gangers and the like are not relevant, you can do whatever you want with them.

When you do a Legion playthrough you need to understand that 'Legion' is not synonym for 'Evil'. A very common misconception.