How do you approach a build?

1 - I figure out what exactly the car is going to be used for.
2 - I figure out how fast I want to go
3 - I then figure out what grade gas I want to be using and its availability. Gas these days have a big impact on your driving habits as well as the octane needed for your particular situation.
After the above I twirl it around in my head seeing if it is going to make sense and if my pockets can handle it