One of the surest, and most frequently followed paths to disappointment in engine building is to wheel the shopping cart down the aisle and buy shiney stuff when you're in the mood, and assume it must all work because it's expensive name brands.
The result is that you get smoked by someone who spent half as much money, and followed a plan. You're buying the dress before you meet the girl.
Think ahead: when do you actually need to install the rockers? About 20 minutes before you order the pushrods. Are you ready to do that yet? The project doesn't go any faster with big boxes all over the room.
Until the head is done, you don't know what you need for a cam.
Until that's done, you don't know what the springs are.
After that comes the rocker choice.
People with 10 years experience make the same mistake, sometimes they even realize it - but not enough.
Another fave is getting a great deal on a very nice piece ("Wow, a low mileage billet .800" lift roller cam!"), and designing the engine around it. The saying during the Civil War was "You found a horseshoe. Now, all you need are 3 more shoes, and a horse - and you're in the cavalry".
