I use the thonky guide to know what clothes are their favorites and recomended, because that way I know they would be happy with them (for example Wolfgang, also my favorite villager HELL YEAH! when he is not wearing modern clothes usually says that the tag is itching and that he can't stand it). After looking on the guide, I choose the one I think they would look cool on them.
I gave the coral thank to whitney, I think she looks cool on it, because I like that design.
I gave Wolfgang the brown bar tee (I don't like the modern clothes that much but that looks cool on him). You can also use the Night sky tee, since is modern AND black, his favorite color, and looks good on it.
I gave Kyle (rock 'n roll style) the Varia Suit so many times but he just don't use it. You can give him the dragon or tiger jacket, or the acid washed jacket (since gray is his favorite color) or the artic camo shirt. Or leave it as he is, since he is already wearing a rock 'n roll outfit, and it looks cool on him.
I gave Freya the Varia suit and she is using it, she looks so cool on it. You can gave her any black rock 'n roll outfit since is her favorite color and style, easy.
I gave Skye the cyan argyle tee, she likes cute and aqua outfits, so this is her favorite style and color.
About the others, I don't know them, so you might use the thonky guide on the rest.
Good luck!