Although the boon seems to be popular, I personally prefer the nail writer. At about $1.50 to buy it, it was not a significant investment. I personally bought a boon and a nail writer, because of how cheap they are (I avoided the TT version altogether, just because I wouldn't feel comfortable with the TT writer...it's far too ballsy for my liking), and have stuck with the nail writer (unless I cut my nails too short...then, I would rely on the boon).
So yeah, it wouldn't really hurt you financially to get a few swami gimmicks that sound like they may be up your alley (I would suggest the boon and nail writer), and just stick with whichever you like more.
Other than that, like mentioned, you'll likely be taking a few trips to the stationary store (after you find out what effects or principles you like).