Success depends largely on the recipes you use that you can find on this forum or online DIY recipe websites.
When I began DIY, only about 30% of my juices were reasonably good. I believe 100% of that questionable success rate was due to choosing the recipes that I chose. Trial and error and inexperience.
You'll need to decide whether to mix your components by weight (you'll need a scale) or volume. Being from the medical field, I chose mixing by volume (ml or cc).
I bought my nicotine from Wizzard Labs. Pg, Vg, flavorings, and mixing equipment (syringes, beakers, bottles) from Bull City Flavors (Bull City doesn't sell nicotine.)