Going Bioactive, but when?

I have been doing non stop research and no one seems to agree. I got a leopard gecko 5 days ago after a ton of research. My goal is a bioactive tank. He or she is approximately 3 months old and weighed about 19 grams when I got him. I will be weighing again soon. He is currently in a 25 gallon front opening tank on packing paper. He has a cool hide, warm hide with a flat basking area, and a moist hide with sphagnum moss. I am intending to supplement UVB light but have been struggling to get shadedweller locally for some reason.

My question is when do I change over to bioactive? Some people suggest not to do bioactive with new lizards because it's easier to watch them on paper. Others say wait until they're almost full grown. Some say throw them in right away. I would appreciate thoughts and real world experience. And I'm still making decisions about soil so feel free to share your favorite substrate recipe.