be careful with the 100mg stuff, but working with the 10ml bottle makes it easy with 100mg ejuice, its all about percentages, if you not good with them get a family member or teenager to help.
for 15mg juice in a 10ml bottle, you would add 1.5ml of the 100mg juice,
so if you want a 50/50 mix, it would be as follows 1.5 ml of the 100mg vg ejuice, 3.5ml vg, 3ml of pg 2ml of flavoring(assuming you are doing 20% flavor).
there is a spread sheet and the ejuice calculator to help, but it really helps to understand the concept first, and to sanity check your numbers, if you are new working with 100mg stuff is extremely dangerous.