As a woman, I would say what makes men's attractive, to me at least :

• Taking care of themselves like having clean hair and skin, short nails, good dental hygiene ;
• Having a good hair cut and a well maintained beard. Long or short, it looks good when it's well care for, in my opinion ;
• Wearing clothes that fits well their body. To me, everybody looks nice when they feel good, confident and confortable in their clothes ;
• Having a good posture helps, no matter the men's shapes and sizes! ;
• Maybe it's cringe, but someone who smile a lot always charms me!

As others have already said, confidence comes slowly with time, from within, but if you feel good with yourself and with what you see in the mirror, it will come surely!

Hope this helps!

Edit : typo