Both Cannabis and Hemp are in a semi-regulated grey area across the globe. Due to the vast and varied legal issues surrounding these products many channels of advertising are off-limits. However, w/o being too blatant it's possible to ensure your brand is well represented.
This posting should be treated as a crash-course and checklist. It's not comprehensive and does require that you do a little work.
First and most importantly is to have a web-site with reasonable quality. You don't need to have a $20k over-hyped, over designed content poor site. Just the core pages (Home, Contact) and make sure your products are well represented.
Using tools like SquareSpace or WIX you can get a site running super quickly and cheaply.
Humans are visual creatures first so use high quality photos! You may want to hire a professional photographer for images of your property or product images.
Another proven method for increasing site quality is to post to a Blog. Your own company news, things you've discovered, etc.
This "SEO" seems mostly like snake oil to me. However, a good site, with the necessary meta-data (JSON+LD, etc) will pull proper rank for your direct terms.
Use the Google and Bing WebMaster tools to verify and validate your site. They will provide guidance on optimization and notifiy you of problems.
Make sure you are using Sitemaps.
Many times the large advertising operations (Google and Facebook) will block businesses in this space. Direct advertising of cannabis and hemp products is very restricted.
You may promote an in-direct item, and DO NOT mention restricted proucts on the landing page.
Social networks have a little more freedoms than traditional advertising networks. Each has rules that are different from the others, some also allow direct advertising (or post promotion).
If you're writing blog posts or press releases then you should post and maybe promote those on each of the networks.
Create a Facebook page for your Company or Brand. Make sure it's got the profile filled out as completely as possible with images, contact information and other details.
IG is all about images. Every single one of your products should have a high-quality image posted. And post a new image from every production run. Use @names and #hashtags to connect your posts to people and topics.
Reddit is more community oriented than other networks. Posts are grouped by topics (call sub-reddits) Simply find communities to participate in and be a good citizen. Up-vote the good content, down-vote the bad. Comments should be wholesome and contain accurate, relevant and useful information.
The Twitter game is pretty easy. Post your content, either text or images (or a mix!) and use #hashtags. What tags to use changes over time, it only takes a little research and observation to get a good understanding. A key point to using Twitter is frequency, post often, daily if you can.