I've tried Nic Base in VG from 3 of the most recommended places on here. They all vary alittle on how "peppery" or smooth they are, as well as their prices vary accordingly.
The 3 I've tried are:
MyFreedomSmokes which IMO is the most peppery, and the least smooth of the 3. A liter cost me $50 for the 100mg Nic Base in VG. I've heard it's especially good to use in Tobacco flavored DIY eliquids.
Wizard Lab Nic Base in VG was quite a bit smoother and much less "peppery" than MFS to me. It costs more than MFS, but it's Organic Nic, and I like that. It vapes great in my fruity juices and in the custard/creamy ones. I've ordered some of it more than once, since I'm adding to my "stash" of nic in my deep freezer!
Nude Nicotine is the 3rd and latest one I've tried. I ordered the sample about 2 weeks ago. It's the smoothest of the 3, and doesn't have any peppery quality IMO. Was also great in the fruity and custard/creamy ones, too. It's the most expensive of the 3. I'll probably order some of it anyway, too, but a smaller quantity than from WL.
No matter which 1 of those 3, or some recommended by other people, you decide to go with...you're still going to be saving a HUGE amount of $$ compared to buying ready-made juice. Plus, your DIY juice will be exactly what you want in every way!