DIY e-liquid
Take a look at some of the material, including the Sticky by Purevapes (Nikhil):
http://www.e-cigarette-forum.com/forum/diy-e-liquid/74109-guide-diy-flavoring.html
Short answer, Yes, taking 36 mg/ml strength and cutting it 5:1 will result in 6 mg/ml.
VG by itself is quite thick, so normally you would want to use some distilled water (the stuff that's like $1 a gallon at grocery stores) or pure grain alcohol (I use a 160 vodka) to thin it slightly.
For flavorings, use the things talked about in Purevapes' sticky or the ones listed in the DIY calculator:
http://www.e-cigarette-forum.com/fo...e-calculator-added-quantity-calculations.html
If you have smoked full strength cigs, 6 mg/ml may be a bit low strength for you, at least at first. It's fine to test with, though equally you can test without using the nicotine liquid. You'll likely want to order some flavorings, and many of the places that sell flavorings also sell PG USP, handy to use when mixing.
(If you mix 5:1 VG to your PG nic you will have juice that's about 16% PG, 84% VG. Many newer vapers prefer more like 80% PG, to get stronger throat hit, unless they have sensitivity to PG.)
Good luck!
The flavorings may take up to 20% of the final juice, depending on which flavorings you use and how strong you want the flavors to be.