For something that has to be washed kind of often use a polyester. For delicate embroidery use a rayon thread. Use a embroidery needle for whatever size thread you are using. The package should show the size versus the thread. Or use a 130/705 for metalics.
The stabilizer for cotton and many of these type embroideries is a tear away. But, there is exceptions if you are going to work on stretchier fabric.