Vegetable Glycerin gives you the glorious vapor from the exhale. It provides a satisfying "lung-feel"
If/when you decide to mix your own, you can buy perfectly good glycerin from Walmart or CVS or tons of places, in "anhydrous" form. Anhydrous means it has no water in it. To use in a vaporizer, you need to dilute it with distilled water by 10% to make "Aqueous Glycerin". AG.
My local vape shop's house juiice is 60/40 AG/PG.
PG is propylene glycol. PG carries over more of the taste and "throat hit" of your juice, especially with regard to nicotine content and flavor additives.
Some people like an 80/20 PG/VG split on a 36mg nicotine juice. That is basically the highest throat hit most people want or can stand. It can be harsh.
I went there in the early going, because I had been a two-pack a day smoker.
It's too harsh for me now. I prefer down into the 50/50 PG/AG and 18mg nicotine juice ranges.
Nobody can tell you what is best for you. It's purely subjective.