That depends on a number of factors. The genesis harvesting rate is 3000 GAIN for 1 Ether. At the very end, the omega harvesting rate will be 100 GAIN for 1 Ether. If you want to purchase GAIN tokens, it is smart to do it as soon as possible!
When you want to redeem your GAIN tokens for Ether during the Harvest, we will use the Spot Harvesting Rate to determine the ratio between the usable GAIN tokens and the available Ether held in the Gain Pool. It is very likely that your GAIN tokens will be worth more Ether than at the beginning, thanks to our trading algorithms.