Hi
@Robbie King, I believe you're doing great by marketing through communities on Slack, Discord, Reddit, etc. as that's a really effective but also inexpensive tactic. Instead of recommending you an educational resource (as I don't really have one anymore), I'd rather advise you to consider implementing the following tools in your current strategy as I'm sure you'll find them life-changing:
promotee.co (for Reddit)
https://www.therainmaker.app/ (for Slack)
phantombuster.com (to export a list of contacts from any community), and
waalaxy.com (for linkedin outreach). Have a look at them and feel free to email me if you need further help! 👍