| Hi Rezan, Doryanthes excelsa is a native of the Sydney basin area and is a relatively easy plant to cultivate. If you are keen on growing them from seed, they are easy to propagate via this method. Some advice RE your plans for germination: It's best not to use a potting mix. Using a seed raising mix is your best chance. Seeds of any type require oxygen, moisture and warmth to germinate, and by using a potting mix for germination you'd be starving the seeds of oxygen, resulting in either slow and irregular germination or not germination and seed rotting. Second, there's nothing to be gained by putting a light on the seeds at night. You can germinate almost any seed in complete darkness as light does not play a role in the actual germination process. Warmth is more important than light in germinating your seeds. Leaving the seeds inside on the windowsil is fine, no additional light is required.
Don't allow the mix to dry out either, and a simple way of overcoming this is to use a capillary watering system. Essentially you water the pots from the bottom and the moisture is sucked into the mix. Your suggestion of using water crystals is fine, but you don't have to. Most commercially available seed raising mixes meet the standards for water retention and good drainage. Personally, I wouldn't add the water crystals to the seed mix as you run the risk of making the mix anaerobic - that is, starving it of oxygen (which isn't good as I explained before).
The way I've cultivated Doryanthes excelsa from seed before is to use separate containers for intitial germination and growing-on. 'Pricking' the seedlings out of your seedling tray when they grow secondary leaves (first 'true' leaves) is the best time to do it. Don't hold them by the stem as you run the risk of damaging them. Hold them by their leaves and gently fill around it with native potting mix as gently as possible to the same level they were at in the seedling tray. Pruning about a third of the root system at this early stage also promotes a healthier root system later. I would use a native plant fertiliser, follow the packet instructions. For a gymea lily to get to the size of the ones in the link, you're looking at up to five years (maybe more/less depending on your conditions). Getting them to flower can be tricky. In the wild their flowers are triggered by bushfires, and this is one method of triggering thier flowering cycle. Another way is to place a round smooth pebble into the centre of the plant, this stimulates the same hormonal reaction in the plant as fire does, just not as intense but still with success. Overall, they're a very very hardy plant. They're drought tolerant and require little to no maintenance once established. There are no known pests that threaten them. Their tuberous growth actually pulls the plant down into the soil to protect it from drought and bushfires, among other things. I'm not privvy to any medicinal or edible characteristics of this plant. Have a look at http://asgap.org.au for more intormation on native seed propagation. Enjoy your gymea lily! Jim | 
