Advice on marketing/advertising myself as a freelancer

Hey everyone, I'm a freelance writer (not a coder) mainly write about advertising technology, digital security and occasionally about non tech subjects.

Basically I wanted to see if any of you who are also freelancers (in whichever digital services category) have any advice on where I could promote myself further at low cost, for more well paying work. Currently charging what amounts to $50 - 70 per hour of work and work is reasonable, but I'm always open for more.

Any suggestions from any of you folks here?