Sex with geckos can generally be identified at around the 6mth time frame, but having said that Rocket and myself acquired some from ari at the start of the year and Rocket is near certain that he can already distinguish, and mine are now starting to become an apparent pair. So 6mths is generally a guide but i guess it all depends on how quick they grow in your care and the amount and frequency of you feeding them.
In terms of breeding- i would imagine around 18months or so, but someone else can specify here.
As for pairing up- in my experience to avoid running the risk of chasing individuals at later dates- i normally purchase a few and then sell off whats not needed.
Let me know when you have more hatchies Danny and i will most certainly get a pair.