I've heard* that "spoke-prep" tends to act like Loc-Tite. You don't want that as you want to be able to true the wheels later on if they need such. Especially with a first-time build. Just a little good oil or grease applied does the trick fine. I've seen many first-time builds stay in great shape, so if you want to go ahead - I won't discourage you.
* - heard -I've never tried it. Too expensive anyway.