I've had the really great opportunity to help a business owner who isn't a manufacturer, but is involved in the cannabis industry and the limitations on advertising are a PAIN. Here's what we've done to make it work and generate leads for ~$1 each.
1. The Website is a big issue
Do you have pictures of cannabis on your site, or even just say cannabis/weed/marijuana/pot? Sorry, probably can't run ads. Obviously you don't want to completely overhaul your website to be able to run a few Facebook ads, this is why we used Leadpages for landing page creation. We basically created our lead gen and product signup funnel within Leadpages to create a Facebook-friendly website.
2. Be sneaky with ad text
You just can't talk about what you actually want to talk about, but keywords like "medicinal", "green", "budding", "flower-power", etc. can be used. Word of caution, if you use terms like "legalization" you may be flagged for running political ads and will have to go through THAT process, or remove that term.
Ok, surprisingly you can be a little straightforward with ad images. You can use leafs, but not buds, just don't make it super obvious what the leaves are!
4. Write Lots of Versions, Be Prepared For Disapprovals
Every time you write an ad write SEVERAL versions of it, and try different ad images - you need to put your hands out like feeling for an invisible wall. Oh, and be prepared when you walk into it. It can feel like you've really upset and/or wronged Facebook when they disapprove your ads, but just edit them! Dumb down the language, get sneakier, change the image - you'll find the ad that gets approved AND gets results.