Hello Kushcod! Welcome aboard!
DIY is really not too difficult. Think about a 100mL bottle (don't start that big, but this will help with doing the math....)
If I have 2% of this flavor and 8% of that flavor and 6% of another flavor, then in that 100mL bottle I will use 2mL flavor A, 8mL flavor B, and 6mL flavor C. That leaves 84mL (100-16) to make up the rest of nic, PG, and VG.
If I want 10 mg/mL nic and a 50PG/50VG juice, and my nic and flavorings are all PG-based, then of the 100 total mL, 50 mL must be VG, and the nic and the flavorings make up the remaining 50mL PG.
So....
16mL PG-based flavors + 10mL of 100mg/mL nic base + 24 mL plain PG will give me the 50mL of PG
Add 50mL VG, and you have 100 mL of juice with 16% total flavoring.
Hard to type this in a spiffy format, but the EASY way to check this is to grab one of those calculators (I use e-juicemeup) Specify your base nic, specify the amount you want to make, specify your ending PG/VG ratio, and enter the flavors as percentages, and it will calculate out the number of mL needed of each component to get you to your goal.
(I often think in 10mL bottle sizes, even if I'm making 15 or 30mL. That just works for me.... I'm also not picky about my ending PG/VG because I basically use PG flavorings and top everything else off with VG - my nic is VG-based)