There is also Sowilo, Munka (MOON-YAH-KHAH), Wunjo, Nauthiz and Algiz. [
The Runic Kabalah]
You can vibrate as many times as you feel is needed until you are satisfied. If you want to work with numbers though I would suggest 8, 10 or 5. For higher reps you can do multiples of either number, so if you pick 8 but want to do more than 8 whilst still retaining it's general energy signatures you would multiply it [8 > 16 > 24 > 32... etc), same for the other numbers [10 > 20 > 30 > 40....]
108 reps is also very effective and powerful, some people consider this too high to stick to on a regular basis though, do what you can.
Hope this helps.