Up Smash is the only one you should do, other than Up Tilt. Down Smash works sometimes, but it's based on the opponent's reaction.
For instance, if an opponent, say a Lucario, is like "oh hey this kid's nairing me WHAT THE **** DO I DO?", you can usually land an up smash or a down smash in this situation.
However in this scenario, you're nairing a Lucario and he's like "oh hey this kid's nairing me I'm gonna counter it with Dair" you'll either hit him with usmash because the hitbox is both above you and faster, or you'll get hit because you tried to down smash him. But then there's some instances where the dsmash is guaranteed, but it's not always easy to see this situations, and in this case, usmash is still guaranteed.
Up tilt is good against characters like Yoshi that have a fast Nair, or when you don't want to stale your up smash I guess. Don't do it that often though, just stick to up smash. Jab is okay out of nair I guess. Don't fsmash. If you know the usmash isn't going to be guaranteed, you can go for a pivot grab to mix it up, since a lot of people will get defensive and shield in this situation.