Growing social media accounts: real experience and questions

Lately I’ve been thinking a lot about how people actually grow their social media pages. Some say it’s all about posting every day and following trends, others insist that promotion services are almost necessary in the beginning. I run a small page and sometimes it feels like the growth is extremely slow no matter how consistent I try to be. Have any of you tried working with promotion platforms or agencies before? Did it actually help your account look more active and attract new people?