I've never grown Amarygia but I've grown Hippeastrums... when the seeds begin sprouting, I just keep them very moist and move them into light. They grow in their start medium for a few months; you can really keep them in there indefinitely or until they are very rootbound.

To keep them especially moist I put saran wrap about 2 inches above the soil; the water condenses and keeps the soil surface constantly wet. As far as Amarygia goes, I don't know it's level of drought tolerance or it's tolerance of lots of moisture. But if they already sprouted, I'd just move them into light and make sure the tender plants don't get dry.

I hope this answer is sufficient until you can get a better one from someone with more knowledge.