If you're eager to make an order right away, I'd start with these things. This will cover the common things that you will probably need with some extras, but it will allow you to take stock of the more specialized stuff for a follow up order (such as flash bulbs, flipper rebuild kit, star posts, post sleeves, etc.). This list is compiled from Bay Area Amusements. Pinball Life would be a little cheaper, but they don't sell game specific rubber ring kits so I went with BAA for now.
1 The Machine: Bride Of Pinbot Pinball Rubber Ring Kit $15.00
2 Flipper Ring - Standard Red 1 1/2 inch x 1/2 inch $1.60
3 Light Bulb #555 EIKO (box of 10) 24-8768 $9.00
3 Light Bulb #44 EIKO (box of 10) $9.00
1 Novus #2 Fine scratch remover playfield polish (8 oz.) $5.99
1 Novus #1 Plastic Clean & Shine (8 oz spray bottle) $4.99
5 Chrome 1 1/16 Grade 25 (Top Grade) Pinball $9.95
10 1 1/16 Tall Post Sleeve $5.50
Subtotal $61.03
Personally, I'd wait until you get the machine to see exactly what you need. At the very least I'd think you'll need a rubber ring kit (cheaper if you buy individual rings, but for your first time a kit isn't a bad idea), fresh pinballs, Novus #1 and #2, new flipper rubber (may be included in kit), and box of #555 bulbs and a box of #44 bulbs. However, it's not bad to wait until you have the machine at home, fill us in on the details, and we'll help you put together a more exact list.