Start out with a palladium kit, and then add the platinum later on once you have gotten somewhat competant making prints with the palladium.
I use pure palladium most of the time, because I like the warmer brown image a bit more. I also use potassium oxalate at 120 degrees to keep the tones warm.
I'm working on an image right now that should have cooer tones, and I'll probably start by using room temperature PO, and if that doesn't do it, I may start adding some PT into the mix, and if that isn't enough then I'll proab;y go to toning in gold chloride. I'm not inclined to use a different developer solution, because I like using PO with the dichromate in the developer for contrast control.
The beauty of PT/PD is that there are so many different means to an end, but that can also be the trap of the process...