My recommendation is that you join a group such as the National Assocation of Rocketry or Tripoli. The NAR is largely about creating realistic models of existing rockets and launching them with premade certified rocket motors. A very good place to start.
 
Tripoli is a little more advanced although the goal of most members is the same but with larger motors.
 
Tripoli does have EX launches, though, where home-built motors are used.
 
Rockets are both simple and extremely complex. That is you can build a simple thing that will whiz through the air. To make it efficient and perform perfectly is  a task of complexity.
 
Think of a car for instance. It is pretty easy to buy a junker that runs and paint  it and put it on the road. To compeletely overhaul the engine and suspension, brakes and steering is more complex. To build an engine from scratch is extremely complex. So it is with rocketry.
 
You probably would not want to try to build a car engine from scratch with no knowledge of how it works, so it is with rocketry.
 
You would search the web for every resource possible, seek out persons who have done it before, and after your knowledge base grows, then would be a good time to think about moving forward.
 
it is a very dangerous underataking too and the reading and understanding of the safety codes is a must.
 
It is also highly regulated by law and you must know these laws and abide by them. The consequences now with Homeland security ar very dire.
 
But despite all, it can be a very rewarding hobby or profession.
 
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