What was the best method to help your baby sleep on his and her own please share experience with me

We are trying to do the Ferber Method and and we did 3, 5, and 8 minutes of leaving her in her crib. For her to try to sleep on her own. There was a lot of crying. till I picked her up and had her lay with me and she went straight to bed. I know I should have been stronger but I felt so bad she was crying bad. She is also going through separation/insurance anxiety. So when I leave the room she starts crying right away or when I leave her with a family member she cry’s so bad :(. Please I need advice