From the photo you posted, the budgie looks to be female, but it’s quite blurry so I can’t say for sure. If you just want another pair of budgies, as mentioned, a pair is better if you’d like to have a larger flock. As Cody mentioned there’s always a possibility that even if there are even numbers of birds with equal gender distribution there may still be conflicts; when adding new birds you have to be prepared to house them separately if needed. If you’re able to do this then a pair of budgies is fine; if you intend to house both pairs separately from the beginning (which may be better to prevent conflict) then a same gender pair would be best so you only have to worry about discouraging breeding for one cage. However, if you’d like to see if they can all get along and be housed together, the best idea is to get a male and female pair like you have now, and then see if things work from there or you have to house them separately.
Ideally, the pair can do quarantine together for enough time that they bond and the two pairs get along well after neutral introductions. This.. is not always the case. There’s no way to predict what the dynamics will be as Cody said above.
In any case, if you have the resources, time, and space for more budgies, then a pair is definitely better as a single budgie may be always trying to join the pair otherwise 👍🏻