I get my Levin's on amazon. $12 each (had to buy 10 to get that deal).
Be SURE it says 36W Levin brand. Just being E26/27 isn't enough, and DON'T believe the ratings. I bought 6 to 8 different kinds. One claimed 54W; it was only 12W. The ones that claim 24W are mostly 12W or less, with an occasional 14W.
I'm an engineer and can measure the actual wattage. The only reliable one I found was Levin brand. It claims 36W, but in fact they are universally 19W. That makes sense if you understand LED ratings from an engineering point of view.
But the 24W being actually 12 doesn't make sense, they're fibbing big time.
Also, do you need 2 of them to get max yield on a dwarf autoflower? I'm not sure yet. I've grown a bunch of plants to maturity, but just can't say if 2 bulbs gives better yield. So probably not. If something isn't obvious, it's probably not significant. Besides, if you have 2 bulbs, grow 2 plants!
When the plant is a baby, and until it's nearly a month and a half, the LED light makes it VERY DENSE. It's wonderful! The full brightness shines on the leaves, nothing is wasted until it starts to stretch. If you grow one with a Levin, and a different plant outside, the outside one will be wimpy by comparison.
Eventually however, they both seem to make relatively the same yield.
How much darkness do you need for an autoflower? None for the 7 varieties I have, except for blueberry.
LowRyder, Amnesia Haze, Northern Lights, White Widow, Super Skunk, and AK47 are absolutely happy with 24/7 lighting. That's why the 19W bulb is better than sunlight. 24 hour light. For blueberrry, maybe 20/4 would be enough darkness to trigger flowering. I got paranoid and did 12/12 when it was clear she wasn't going to flower without darkness.
Blueberry is disappointing under a single LED light. Too stretchy, lives 5 months+. Super Skunk and Amnesia Haze can completely finish in 2.5 months.
Soil: Very important. I didn't believe it at first. But marijuana REALLY needs the nutrients. I cooked up a formula based on all the advice I found in here and on the net, and it makes perfectly dark green plants until the budding, and the budding is very dense. No change in nutrients the whole time, no need to switch from grow to bloom.
Watch out for getting anxious and picking buds too early. They'll be less dense than what you can buy. Just let those buds mature until most of the hairs turn brown, and the trichomes have some amber ones. Otherwise people tend to pick too early at first, and then complain the buds don't get dense and hard.
Read up if you need to make soil, but pay attention to: Edna's best or Fox farms soil. Worm castings. Bat guano (get one that is low in nitrogen, so it's for the flowering stages). Epsom salts, Kelp Meal, and osmocote (1TB per pot).
Results of that: no need to change nutrients, plants are green and dense till flowering, and the buds are so filled in, you'd have a hard time crushing one with your hand. Might not be the mellowest smoke however, people like to flush nutrients at the end, this soil combo won't flush so well. Frankly, I don't care if the smoke is mellow or not. In the 70s, they put jet fuel in there, and it seemed better to me back then.
If you don't like having hundreds of gnats, break a mosquito dunk onto the top of the soil. Takes 2 weeks to fix an existing infestation, but it does work well.