Since antiquity, the most satisfying tools for accurate cutting stone and marble were a mosaic hammer and hardie. Although those same tools are still in use today and remain the preference of professional mosaic artists, other tools are also in use such as chopping machines and nippers.
A mosaic hammer and hardie for glass smalti are quite expensive, so, if you think you are not going to use smalti a great deal you could buy a mosaic hammer for marble (if you keep it sharpened it may be used for smalti too) and a hardie for glass. If you are going to use gold smalti often you need to buy both the tools for glass otherwise you would waste too much material in cutting it.
To mount the hardie, you will need a log of hardwood like Oak or Douglas Fir about 10-12 inches in diameter. You chisel out an opening to seat the hardie after you have sealed both ends of the log with wood glue to prevent splitting caused by drying.
You will also need a set of tweezers for placing the tesserae. Finally, many people use nippers for cutting and prefer those to hammer and hardie cutting methods.