One thing that is particularly valuable to use when building your first few builds, is another similar gun to hold in your hands. For the "now what is it I like and dislike about this gun" moments that seem to come up at many stages. It could be a half stock or full stock. They all have barrels, ram rods, lock panels, butt plates, and some have patch boxes, inlays, and toe plates, along with other embellishment. They differ in other respects, but will give you a "bird in the hand" to look at and hold while performing certain tasks that the books and pictures do not. Where they differ is in their architecture, but the basics are the same. If you don't already have one, see if you can visit some place that has some, or maybe you can borrow one from a friend for the duration of your build.
Most people start out with the "sand and assemble" kits from Lyman, CVA etc. While a good place to start, they don't teach you a lot about building. A next step is a parts' set. Some have locks inlet, and some do not. One advantage to them is that the basic shape of the gun is already pretty much done for you. The disadvantage is that you have to choose from what is available, but there is a pretty wide selection. Most do not give you enough extra wood to do very much alteration regarding stock shape, cast off, twist, or comb height and shape, and they usually come with pretty thick webs, but there is a lot of wood that will still need to come off none the less. The parts in them are pretty generic too, so most of them will need some alteration to fit the exact model or gun you are looking to create. Just remember to make the parts fit the gun (regarding style and location) rather than the other way around.
The last step is deciding what gun you want to build, and then go shopping for the appropriate parts. You may or may not choose to have someone else inlet the barrel for you for about $90 last I checked. Dave Keck (and probably others) will do it if you supply him your barrel and your own wood. When you go that route, that gives you the most flexibility to create what ever you want, and if parts are not available from the well known supply houses, you can always make them. Most first timers choose not to make their own major parts that require special equipment or advanced skills, (barrel, lock, trigger guard, butt plate etc.) but it's been done before. Just remember that the more work you leave for yourself to do, the more places there are to make a mistake.
Good luck. You'll enjoy it what ever you decide to do. Just remember--it's a hobby, not a job. Enjoy it for what it is, and be glad for what it is not.