I personally would get two boys, two handreared boys that is.
Females are quite often nasty and like Blues says, seperate cages would be best because who says they are going to like eachother?
If you were really serious about breeding later on down the track, you could set each male up with a girl but I must warn you, breeding is not as easy as most people think and if you just want two budgies to enjoy and to have as pets, why go for a male and a female, once again I would suggest two males.
Just my two cents worth
