What does the Bible mean by telling to dress modestly?

To me it means women should dress with decency as not to invite unwelcome advances by men. That is not to say women cannot dress in the fashion of today, just not wear clothes so tight or bare that leaves nothing to the imagination. Also, when privileged by wealth, women who live in a generally poor area should not flaunt their own expensive clothes. They should only wear those when among equally wealthy friends or family. I don't take the reference to braided hair, gold and pearls literally. Remember St. Paul lived 2000 years ago and maybe at that time braided hair, gold and pearls were worn by certain types of women.

It means that women should wear apparels that will not lead men to think lustful thoughts. Respected women wear clothes that cover their private parts and not expose any part. In addition, that women does not over-decorate themselves to show off. You can search for other meanings in your bible study!