A lye discount basically means a % discount for the oils that you are using so that you don't have excess lye in your finished product. Basically in theory, if you use exactly the amount of lye needed to saponify the oils, you would have no room for error, and may end up with a lye-heavy soap. I would say most use at least a 5% discount, meaning that you would use 5% less lye than is actually needed in order to saponify your oils. It is for safety, as well as leaving some oil in your soap for more moisturizing.
I hope that I explained this okay. It took me a long time to figure out what everybody was talking about with the lye discount or super fatting.
As far as the oils, each oil has a property, meaning that some oils are cleansing, some are conditioning, some are bubbly, etc. Some are softer than others. Coconut is high in cleansing, hardness and bubbles and to some (me) extremely cleansing. Too much coconut or any cleansing oil leaves my skin crawling and itchy. The three basic cleansing oils are Coconut, palm kernel, and Babassu. They are also hard oils.
Olive oil, on the other hand, is extremely moisturizing, and when given cure time, will make a hard bar, but low on bubbles. It does take longer to cure to get the hardness.
This will help you a bit with the oil qualities and is also one of the soapcalcs that I use and gave me tons of insight as to how to figure recipes.
http://www.soapcalc.com/soapqualities.asp
Hang in there and as long as your lye is discounted enough to avoid a lye-heavy soap, it is all a big experiment as to what is right for you!
You will do great!!! It is exciting and SO much fun! Just take your necessary precautions, gloves, goggles, long sleeves. I wear a mask because of the fumes. No kitchen blowing up allowed :wink: 
