You’ll want to say a personal and sincere thank you to everyone who has come to your wedding and generously given you a gift. And a written thank you is expected even if you said thanks in person at the wedding.
Writing out a hundred plus thank-you cards is time consuming and it’s a job that both you and your partner should tackle together. The easiest way for you to thank your friends and family and for him/her to do the same. Split joint friends between both of you.