To craft a Glimmer Rafflesia, you just have to keep doing the Grow Dark Seeds craft in the Greenhouse. If memory serves, that's the rarest plant of all and may take quite a while to get.
In general, for the Main Storyline goals that aren't timed, the HUB is the best place to go for information. All the goals are compiled with helpful tips of what you need to do, what goals are connected and there's even links to the discussion threads on the goals as well.
Main Story HUB: https://forums.storm8.com/showthread.php?94062