well, what kind of tone are you wanting to get out of this guitar?
wood type makes a world of tonal difference.
mahagony(purty expensive tho) it very dark and warm.
basswood is very light and soft, it's in between mahagony and alder on the bright scale. as a result, it's very midrangey.
alder and ash are near the same, but different. ash is very bright and under high gain it can be really harsh. i love alder. it is close to ash but not as bright. the best strats are made of alder, imo
poplar and ash are pretty close the the same as far as tone goes, ash is better. poplar is about as cheap as it gets, i think.
basswood is very versatile and cheap. it's also easy to work with because it's soft. this is what i would recommend to you if this is your first homemade guitar. just don't install pickups that are very high in the midrange, unless you like tons of mids. high mid peaks bug me. also keep in mind since this is a very light and soft wood, it tends to ding really easily.
good luck and i hope everything goes well,
cory