Being a techie spod I already had my own domain so it made sense for me to set up a blog on my existing webspace. I found Wordpress to be the best for that; easy to set up and straightforward to use, but the self-hosted blog isn't a solution I'd recommend to someone who isn't reasonably
au fait with keeping a website.
While you're learning the ropes, it's far easier to sign up with somewhere like
Wordpress.com or
Blogger.com - as to which of the two you choose, that's up to you. I like Wordpress, but I've never tried Blogger so I can't compare the two. I'd say if there's a chance you're ever going to want to host your own site and blog and you're thinking of using Wordpress for that then it would make sense to use their hosted blog since it's likely to be easier to import the data across when you come to move. If you have no such plans, then I'd recommend you play about with both and decide for yourself.
That's a hell of a long winded way to say "I dunno", isn't it?
Edited to add: By the way, I for one would be fascinated to see your blog. I've never heard of the methods you're planning to use, but they sound fascinating and it's always exciting to see new stuff. Is the "moon" method related in any way to biodynamics? I knew a farmer in Germany who swore by biodynamic methods, oh, sixteen years ago and the moon thing rings a bell...