Its the Space Marines (sad? but) true!
Buy the knew [URL="http://www.games-workshop.com/gws/catalog/productDetail.jsp?catId=cat440270a&prodId=prod2220 002a"]"Strikeforce"[/URL] Box and you got a whole Army to start with for less than 200,- € add the Codex and it´s 250,- (you can get it cheaper if you buy it at your local store or mailorder discount). Add in the basics for TT: Paints, Basing-Stuff, Brushes, Glues etc. this will eat up easy another 50,- €.
But the best way to start is simple: Look at the armys, read something about the armys, read some 40 K stuff and choice the army you like best - don´t look for playability. Buy some stuff (roughly about 500 pts), build it, paint it an make some games.
And: Play Chaos!