How much PE to use depends on how dark you want the color to be. You don't really need much, maybe 1/16 tsp per 1 Tb EP. You'll lose some of the PE if you emboss over paper. I prefer to tap the mixture back into my container so I don't lose the PE.
The best way is to experiment. You can also mix colors to create totally new colors. That is lots of fun. All have a metallic shine that's different and brighter than regular EP.