I always thought, Astarion was the most popular romance, since the internet is full of him. If you look for anything BG3 related, chances are, you stumble across some Astarion fanart, fanfiction, Astarion comments ...
I find Gale especially hard to romance - I did try to do all romances at least once. The prerequisition for his romance is the weave scene and out of 15 playthroughs, I did manage to get that twice and I rested a lot. Not that I want romance Gale that badly, but I like to try out the different options in the weave scene. The problem is, that Gale gets approval too quickly. He normally is already high approval, when you do the harpries quest. And then you have scripted events while resting, like Raphael, Astarion trying to snack on you and so on. I find it nearly impossible to do the Gale romance.
But if I wanted, I could have romanced Astarion in nearly every playthrough but one (I didn't want to, but he offered) and I always play good aligned. You can get points, if you are understanding of his problem, be nice to the owlbear cub, declining Raphaels offer (and be adamant about that in later conversations with different companions), help Karlach (I always help her), choose deception answers... So I'm mostly in medium range with him, which is enough for the romance. You will probably run into problems later in the game though.
