Building it yourself is half the fun!! I had 2 before I started modifiying, that way if I messed one up I could salvage parts off the other. I started small and did more as my knowledge grew. Also some mods I could not appreciate at first wound up on the "need to do" list but we are getting ahead of ourselves. If you get a wally world carbine you can modify the stock to make it look cool, which is a lot of fun, and put in a couple parts to improve the trigger. A hammer, auto bolt release, extended mag release, extractor and bolt buffer are good basic mods. After shooting it awhile you might decide to work on that trigger some more. It will be easier to do at this point because you've gotten some practice putting in those parts. You will have taken it apart so much by this time it will have become second nature.
Then you'll want to start thinking about a new barrel. This will lead you to research on how to swap barrels, you'll find out about different v-blocks and what they do, and you'll start reading about bedding and floating barrels. You'll do some things wrong and you'll post some questions, we will be here to help. If you think a questioin is too stupid to ask don't worry, I've already asked it!!
Once you get that first one shooting and feeling the way you want you can move on to a fancy schmancy laminated stock, by this time you will have a better idea of what style stock will suit your shooting purposes. Will you want a bench gun or something to tote in the woods? You might find your wants may change after working on that first one. You might be ordering those better shims and pins because what seemed like too much trouble on the first one will be your new challenge on the next one. I would recommend the pins last because you might be taking it apart quite a bit and those new oversized pins will all of a sudden become loose, don't worry, there's always kidd pins. What seemed hard on the first one will seem ridiculously simple on the second.
So I recommend getting 2 wally worlld specials, one to cut your teeth on and one with more specific goals in mind. You'll need a few shoeboxes and some baggies for the extra parts you're goiing to have and a small work area, like a desk or table, that will be permanantly cluttered with your work in progress. Dining room tables work great, not the one you eat at every day but the "nice" one that only gets used during holidays. The chandalier will provide nice even lighting but you'll probably want a task light also. Start claiming old towels now, preferably plain colored so it will be easier to see small parts. Tell you're wife you are ashamed of the old towels, that might score you a few more when she gets some new ones. Small parts don't roll off towels as easy as bare tabletop. Disposable food storage containers come in many sizes and are handy to sort and store you work in progress. Some small cheap tools will come in handy, I recommend a drift pin punch set, screwdriver and bit set, dremel type tool, might be the only time you use it but I find it indespensible, allen wrench set that includes the entire spectrum, like 9/64 and stuff, and one of those magnetic retrival tools. I got a magnetic parts bowl at harbor freight that is pretty handy (harbor freight is my friend!) .
Also some kind of folder to print out more used instructions and diagrams. I started a few files on my computer so that when I see a good tip I cut and paste it into that document so I can easily find it. I have one on stock tips, bedding tips, ect, you get the idea.
So basically you'll be starting small and building on that knowledge as you go along. Oh, sometimes these things are fun to shoot also!