You can get that mad crazy metal box of Every color paint Citadel makes for $250 . I also recommend these Really nice Brittish Sculpting tools, they look like paint brushes but the tips are nylon - about 30 bucks for a set of 5 and they have soft, medium and hard tips. I use the hard tips and they are the best sculpting tools I've ever touched. (sorry can't read the brand anymore Mine are coated over with years of Marine epoxy putty)
Flex shaft for your dremel if you don't have it and get some router bits from the Home Depot, I can create my own ball sockets with some of the bits I got there. Well worth the expenditure. A 4lb tub of Apoxie Sculpt for about $30 (before shipping) Some good wet dry sandpaper in the high grades like 1000+, a couple of packages of Sheet styrene (including clear) more ink cartridges for your printer so you can print your eBay invoices and postage labels. umm ummm some figs, and save about 40 bucks for Black Arachnis... (but you gotta wait until after June)
wow, wish I had $500 to blow on customizing!!