Well, the first thing you do is decide what caliber you intend on using, not necessarily what cartridge. If you want a .30, .338 or whatever. Then you order your barrel as soon as you've decided on that. Because it's gonna take you 3-4 months to get your barrel. Then you start researching smith's and find one that specializes in making precision rifles (as in he's the guy that all your local BR/High power and F-class guys are using). While you're doing that you can start looking for your donor rifle/action and possibly stock. If you're lucky you can find a 40X, Sendero, VSSF etc. that already has a HS precision stock or Hogue OM with full bedding block on it for a screamin' deal. Or you find an old 700 that has a beat up stock/shot out barrel but a solid action on it with little/no galling on the lugs and a tight lock up. Or whatever other 700 you can find for a screamin' deal, you can always auction leftover stocks/barrels etc. on one of the auction sites and get a little smithin' cheddar back. Once you've got all that take barreled action/barrel/stock to smith and get-R-done.
Then of course you need to get your scope, rings and bases. Shortly after that all your friends here at LRH and your smith will probably convince you to spend another grand on all the reloading and shooting equipment that you really
need. And then my friend, another rifle idiot is born.