When I started a couple of years ago, the recommendation was for a pack-a-day smoker was 16-18mg/mL at 2-3mL/day using a cartomizer or first-gen clearomizer. I was there for three months or so, adjusting to the fact that I could stop vaping when I was satisfied, compared to smoking the entire cigarette because it was already lit. Then I upgraded to bigger and better clearmizers and mods, decreasing the nicotine concentration whenever I started to get the dizzy feelings. Two years later, with a Kanger Subtank Mini and self-wound coils at 1.5ohm, I go through 4.5mL/day at 1mg/mL. If you think you're vaping too much throughout the day, then up your nic level until you're satisfied, decrease it when you get dizzy.
Don't be afraid to mix juices of a different concentration but same (or even different) flavours together. Most stores carry a 0mg, 3-6mg, 8-12mg, 15-18mg and a 24+mg so that they can keep a minimum of inventory on hand. A bottle of 18mg and a bottle of 12mg of the same flavour and equal volumes makes for a really big bottle of 15mg. A bottle of apple pie and a bottle of vanilla ice cream makes apple pie a la mode.