You need to bring a realism to the character. It’s best to use character questionnaires to help you get a better grasp on the personality of your character. I will link a few threads below to help you out. Most of the time you have to ask yourself “What would you do if you were your character?”. Keeping that mental note when asking yourself questions will help with making characters. Never forget to add flaws! It’s fundamental element of the character which makes them more relatable. These are a handful of top threads that go over a character’s personality. When it comes to clothing I would look for clothes that aren’t in a face claim. It’s always best to pick them out separately because like you have run into the clothing doesn’t match your character. I would also suggest roaming the RP section which can help with getting into more detail with your characters as well.
https://forum.shanniiwrites.com/t/interesting-character-exercises/196
https://forum.shanniiwrites.com/t/discussion-worst-romance-tropes/7933
https://forum.shanniiwrites.com/t/extra-long-sheet-of-character-questions/4712
https://forum.shanniiwrites.com/t/questions-your-character-hates-getting-asked/7867
https://forum.shanniiwrites.com/t/qutsions-to-ask-about-your-character-the-ultimate-trait-list/3501