You would be better off waiting untill your little one is old enough to sex. Factors to consider with having two geckos togehter is:
the potential they breed if your little one turns out to be male
bullying and dominance issues if you have two females that are not compatable
Is your accommodation big enough to house two?
also the new addittion would need to be quarantened before introducing to the existing gecko. I would do lots or reading on the issues of co-habiting just to make sure you are aware of all the posibiltys and can make the best decision for both your gecko and you
Thanks for your info! yes my tank is 20 gallons. I will read up on the topic. I know about the quarentine. i got him on the 26th of December they said he was a month old. Is 10 months a good age?
Negative. A 10 month old gecko will be nearly adult sized, and thus there's a huge potential for problems between the two. Your youngster will likely be bullied to the point of starvation.
Reptiles are solitary so they do best alone. Two females will sometimes tolerate eachother, but bulling will occur over food most of the time. You should only keep geckos of the same size together, but what if one turns out to be male and one female, or worse two males. I would wait till you know the sex and go from there.