I just went back to my post long time ago:
Here is something to consider:
Getting a gemstone egg pedestal is as rare and as exciting as hatching a gemstone dragon because you can never breed 2 gemstone dragon together unlike any dragon, so once you miss the egg, you'll never get it until next year. Yes you'll miss some gem, but that is only 1 gem per week/4 gem per month, that is just too little, that is not something to worry about. And there will come to the point when you'll get more than one gemstone dragon per month, your gemstone island will be full even before all the gemstone dragon be introduced, you have no choice but to sell it, then there will come to point that you'll regret not having an gemstone egg collection.
Here's my simple rules: 1st goes to the island, 2nd for display, 3rd or more goes to the island. You already have one Topaz in the island, why need two, you still don't have Topaz's egg pedestal, then display it.
but it's your choice, some like collecting stamps, some think it's just a piece of paper, same thing on collecting eggs, some are just not fond of collecting eggs.