Hello, I'm a lefty.
I mostly use pendulum serves, so my most common serves against righties are short underspin to the forehand, long fast light side-underspin to the backhand, long side-topspin to the backhand, short side-topspin to the forehand, and extremely wide sidespin to the forehand (like He Zhi Wen).
What serves you will do will depend on the player you are up against. Not only that, but what you will serve also depends on how good your own serves are and what your strengths are.
If you are good at disguising serves, you can serve a lot more side-topspin and no spin and get away with it unpunished.
If you are good at opening attacks, you can serve short underspin to easily get the chance to attack first.
If you are good at counter attacking, you can serve long and counter attack.
If your opponent is good at looping serves, you can serve short to prevent that from happening.
If your opponent is bad a flipping short balls, you can serve more short topspin.
If your opponent like hang around near his backhand corner, you can serve really wide to his forehand (not too long, make him step in).
If your opponent is wary of those wide forehand serves, serve long and fast to his backhand (I found that disguised side-underspin works best).