I don't know who you're asking, but I'll give you my opinion of several places below. If you're wanting to end up with a 30PG/70VG ratio mentioned in your first post, and you're planning on using only 1 or 2 flavorings (that will give you a minimal amount of PG)...I'd recommend ordering your Nic Base in VG. That way, most of your VG content will already be in your Nic Base, and you won't need to buy so much of it. You'll still need to buy some plain PG and some plain VG, but not as much VG.
Because you want to make your final liquid at 1.5mg-3mg nic, and it's your first time even trying DIY...I'd order maybe a smaller 120mL bottle of no more than 12mg Nic Base in VG to start with. When you input that starting Nic at 12mg into the calculator, and then your final Nic content you want in the finished liquid...you'll see that you'll use only a small amount of it to make each 50mL bottle of finished liquid. So that 120mL bottle will make a bunch of finished eliquid at your 1.5-3mg. I did something similar to that with my first DIY liquids. Because I wanted to end up with 6mg Nic in my final liquid...I ordered a 120mL bottle of 24mg Nic Base in VG. I also ordered only 120 mL of PG, and got a 177mL bottle of VG at Walmart for $3.86. I've been able to make quite a few 50mL bottles of finished liquid, and I'm still not even out of my original PG and VG I bought!
Lots of places have Nic Base, PG, and VG. Because I was ordering my flavorings from Wizard Labs...I ordered my 120mL bottle of the Nic Base and my 120mL bottle of PG from them at the same time. Got the 177mL of VG at my local Walmart.
When/if you decide DIY is for you...then you could order in much larger quantities, and some of the places that I've found the best deals then were:
Bulk Apothecary for PG and VG by the gallon. I paid $38.32 for 1 gallon of each, including S/H from Ohio to FL. That was a great deal on that! They also carry it in smaller quantities, too.
Nic Base I ordered from MyFreedomSmokes (a supplier on ECF), and they run sales on it every now and then.
There are other places as well, that many people here use. 1 is mentioned above (EcigExpress), and there are many others.
I hope that made sense and will help you.