Not bits, but just as important, I started out buying a full set of PreciseBit dewalt 611 collets to be able to use whatever bits I choose regardless of shank size. I have been very happy with them.
For bits, I did not start with any of the inventables kits. Instead I started out with some inexpensive 10 packs of 1/8 and 1/16 end mills and ball nose from ebay. I also already had a 5/8" 90-deg router bit from a craftsman router bit set. They have been great for learning, and I wasn't afraid of breaking them because I had plenty of extras.
These bits have been great for learning:
1/16 bulk bits from ebay user roguesystemsinc:
- 1/16" solid carbide end mill LONG 3/8" LOC 4 flute square end USA 5 pieces
- NEW 1/16" Carbide End Mill LONG 3/8" Cut 4 Flute BALL End USA Made 5 pack
Now that I've started doing some work with more expensive materials I have been investing in PreciseBits (http://www.precisebits.com/). Everything I have bought from them has been exceptional. I've gradually built up this collection over time to ease the blow to the wallet.
For profiling / pocketing:
1/4 in. (0.250 in, 6.35 mm) 2-flute fish-tail end-mill, 1.40 in. max DOC, 4.0 in. OAL, 1/4 in. shank
V-tip carving / engraving 4-bit set (1 each 30°, 45°, 60° & 90° tools)
For sculpting/carving clearance passes:
1/4in (0.2498 in, 6.345 mm) dia. 4-flute 0° Tapered Ball-nose Carving bit, 1.00 in. max DOC, 1/4 in. shank, 2.5 in. OAL
For sculpting/carving final detail passes:
1/32in (0.0313 in, 0.775 mm) dia. 3-flute 6.2° Tapered Ball-nose Carving bit, 1.00 in. max DOC, 1/4 in. shank, 2.5 in. OAL
For cutting plastics:
0.1250 in. (3.18 mm) micrO-Flute 1-flute upcut thermoplastic cutter, 0.250 in. max DOC, 1/8 in. shank, 1.50 in. OAL
Other Specialized Bits
Some specialized bits that I have purchased for various projects.
From Drillman1 on ebay for engraving coins:
- 30 DEGREE MICRO CARBIDE ENGRAVING TOOLS - NIB Kyocera Microtools Kyocera MIT
- 60 DEGREE MICRO CARBIDE ENGRAVING TOOLS - NIB Kyocera Microtools Kyocera MIT
- 90 DEGREE MICRO CARBIDE ENGRAVING TOOLS - NIB Kyocera Microtools Kyocera MIT
And some misc bits from amazon for engraving: