Taphthartharanth is the Spirit of Mercury. Calling on it alone from what I heard from others is not going to be very powerful. I call on it together with Tiriel when making talismans or petitioning Mercury. Some writings also mention Raphael and Sadayel being called together with Tiriel and Taphthartharanth. Mercury's number is 8 and I use 8 white, or geeen or rainbow colored candle and frankincense as an offering. To get the most out of it do it with Mercury direct , essentially dignified, preferably on the ascendant or 10th or in the house representing the area of your life you need help with and in the day and hour of Mercury, and not in an applying square or opposition aspect from Mars or Saturn. Also watch for combustion if not in Gemini or Virgo, from my experience only Sign gives chariot. Ideally you have the Moon trining sextiling or conjuct it. For invocation you can get Warnock's planetary invocations and the petitional part from the Picatrix and modify it according to your own needs. I have used it for myself for getting better business ideas and income, it definitely sharpens the mind, worth working with it even only for that. The most I did achieve was doing a petition on behalf of a friend who was having trouble finding work. He did his Solar stuff I did my mercurial stuff and he got a good job. That time I also called on Clauneck too, but Clauneck is very fast so you you really have to be ready for the interview.
You are definitely on the right track, but you still have much to learn. Definitely worth giving it a try to see if it matches with your energy, personality and natal chart(if it doesn't you may need an exaltation degree talisman made).
Taphthartharanth on it's own is IMO weak, but a wider and bolder and well researched connection with mercurial spirits is worth it. The good thing is that you already have worked and read about Taphthartharanth, and that should make it smoorther to attempt bigger workings.