Firstly, I would recommend buying my starter kit here. It’s really good value, and will give you the vast bulk of what you need to start silversmithing!
Silver
Cooksongold – Great for silver supplies, wouldn’t recommend for purchasing of tools (ebay/amazon are often cheaper)
If you are starting out, I would recommend purchasing bezel wire in both widths (0.3 cm and 0.5 cm). I’d also purchase some ring wire (3x2mm D shaped wire is a good starting point). I’d also purchase some sheet silver, I’d also go for 10x10cm of sheet silver that is at least 0.4mm thick (If you can go for 0.5mm even better).
Metal Clays 4 You – Good for some unusual wires, solderable accents, etc.
Curious Gem – Good for pre-fabricated bezel cups, also have a large silver charm selection.
Cabochons
For cheap and cheerful, I’d recommend ebay. I often purchase in bulk from Indian sellers, as these are the most affordable cabochons. I’ve never had an issue with a package not turning up.
For slightly nicer/higher quality gemstones Etsy is a good bet.
Kernow Craft also has a great range, but they are on the more expensive side of things.
Other Tools You May Need
Grinding + Polishing Dremel Pieces
Small Pots– For storing your solder chips
Pyrex Jug– For quenching your pieces
Tools To Think About Long Term (Buy As + When Needed)
Doming/Dapping Block– For making spinner rings/other 3d objects
These Triblets – Great for making bezels for unusual shaped stones
For Stamping Projects
The most famous brand is Impressart, which can be purchased from Cooksongold. However, this seller does knockoff ones for about half the price. You can get some amazing stamps designed for leatherwork, however these are more often than not, not made from hardened steel so will not create a good enough indent in your work.
I’d also recommend these Mini Punches