Yes, perlite is organic. Its volcanic rock that has been heated and puffed up like popcorn. As for the soil mix, you only need three things: Soil, Perlite (or vermiculite), and worm castings using a 5-3-2 ratio. Terracycle is a really good brand. They sell it in granular and liquid form. The granular castings is the one that comes in a recycled milk carton. Its good stuff, and its very forgiving. You mix it into the soil, then after a few weeks you follow it up with with the liquid stuff. I feed my plants worm tea once a week.
I've read research papers that mentioned that worm castings contain an enzyme called chitinase which breaks down the shell of insects. Not only does it aid in breaking down the material, but also acts like a natural insect repellant. I've also been seeing some of the better worm casting companies feed their worms with kelp, oranges, and misc fruit. You need to be a little picky about the brand you buy, because some companies just feed their worms paper and sawdust. However, if the worms are feed well, the castings will have everything the plants need.
Later on if you feel the need to add anything else, go for any balanced fertilizer that contains beneficial organisms like mycorrhizae & ectomycorrhizae. I'm a big fan of Kelloggs Starter Fertilizer for this very reason. Plus they are a local company from where I live and you can find their product at HomeDepot.
Best of luck to ya.
