“You’re so brave to wear this outfit”
Well, this is an indirect ‘compliment’ on their choice of outfit. You’re telling them that you would never wear what they are wearing. You can just say “Your outfit looks amazing” or “You look gorgeous in this outfit”.
“You should smile more often”
Well, it’s like telling someone that they always look gloomy. Asking people to not be sad doesn’t really make them happier. Instead, you can offer your support and express your concern by simply asking “How are you doing?”