If you ask me, I'd recommend going for 4-Gladiator above the rest. This is for a rather simple reason: Gladiator is more "stable" than the other 2 sets.
4-Gladiator provides great normal attack damage, while being only slightly behind in plunge damage.
Not only that, it's also easier to play with normal attack rather than plunge
After the Keqing disaster, I decided to immediately build her anyway. I took Black Sword from last month's Battle Pass because I don't want the rest of the weapon, and Keqing seems to take that personally.