Moving to DIY General Discussion...
Hi, and welcome
@Hitstick707! Your question has a simple answer, and a more complicated one...
For 30/70, you want 4.5 ml of PG, 10.5 ml of VG. To get there with your flavors and nic, you need to know whether your nic is in a PG or VG base (or a mix), and what strength you want to cut it to. Also, the vast majority of flavorings are PG-based, so you'll want to subtract any flavoring you add from the PG in your final mix.
Example: I use 60 mg nic at a 50/50 blend. I want to make a 15 ml bottle of 6 mg liquid with 10% flavoring at a 30/70 blend.
First, I need 10% of my 60 mg nicotine to end up with 6 mg - that's 1.5 ml. Since I'm using 50/50 nic, that's 0.75 ml of VG, 0.75 ml of PG.
Next, I add 10% PG-based flavor, or another 1.5 ml - now I have 2.25 ml PG, 0.75 ml VG.
Now, I need another 2.25 ml of PG to get to my 4.5 ml target, and 9.75 ml of straight VG to get to my 10.5 ml target.
Make sense?