You can save 11 percent in taxes buy building your own. A stripped lower receiver does not require a federal excise tax but as soon as one part is installed into a lower receiver it falls under federal Excise tax category. So say you purchase a complete rifle add %11 in taxes to that. Or if you purchase a complete lower your just charged the tax for that portion of the rifle.
I prefer to completely build my lowers and purchase complete uppers for them. The lowers are super easy to build (install parts) and helps you learn the inner working of that part of the rifle.
NOW either way down the road it can be expensive if you start changing the original platform.
I spent 6 months researching my first build trying not to buy twice on any portion of the build. Part of the problem is you won't know wether you like the set up you chose until you build or buy it. My first rifle I've changed a few times because it's purpose built toward one type of shooting and goal in mind. My other rifle is the same as the day I built it with exception I've painted it twice, different camo schemes. The only other thing I plan to do is add an optic to it.
My third build I'm working on is purpose built also. Hopefully with careful planning I won't have to change anything after it's built but I won't know until it's done and I spend some range time with it.
For some people it's easier if they have no particular goal in mind, other then to learn to use the rifle, to build/buy a basic rifle and go from there.
Good luck regaurdless!
Keep us posted what you decide to do.
Side note: If you just want to build a simple but nice rifle check out PSA (Palmetto State Armory) they have excellent deals and alot of kits to choose from. Rifle Kits - AR-15