I have the same router (DW618). I started my bit collection with a
1/2" shank, 15-piece set from MLCS, at $35 in their "Web Specials"
section. Free shipping. Granted, these are definitely not
top-of-the-line bits, but I haven't had any problems with tearout or
rough cuts. One bit broke when I was maybe using it a little hard, but
MLCS quickly replaced it free of charge (2-year warranty). At slightly
over $2/bit, just play around with these for a while, see which you use
most, and then get some good ones (Amana is probably the best I've
used, and I've also heard good things about Katana by MLCS, Infinity
Cutting Tools, and CMT).
Good luck and have fun,
Andy