A worm bin should probably be item 1 on the list of any organic farmer.
No matter the size. Even if you have a small 1 cloiset grow, just get a smaller worm bin. But the earth worm castings are so important and valuable in organic growing, even if you discount the worms (which are also highly beneficial).
It's also high on my list, haven't started one yet. I was fortunate to find a place where you get 40 liters of EWC for 8 bucks which is absolutely fine. But that is one channel, the next best offer I found was around 12 bucks for 30 liters.
And you never know 100% with the quality, what did the worms get fed, etc.?
With increasing size of the grow, a worm bin becomes an increasingly beneficial factor as well, so I would really only skip it or buy the EWC if you either have a very small grow or simply don't have the space to run it.
Otherwise, always worm farm if you want to organically ganja farm