Fungal wood is easily obtained through the weird alien ball trees where the Shadomanes spawn. Craft up a bunch of those, check out my favorite method to catching

Fish on YT by CJ the cheese DJ

Sanguine elixirs DO work on passive tames like these. You just have to give it its first feed and when it's ready for the next, "eat" an elixir and BOOM 30% extra! Arrow this to the sky!