I would suggest start off with a budget for web development. You’ll definitely need an online presence in this day and age. It’s a great place to post photos of your studio, a floor plan, your services offered, song and mixing demos, contact details etc.

Next take some of that money and invest in a good SEO company/person. They can work wonders with your organic and paid clicks getting you top Google Ranking.
Thirdly, create some great looking business cards and start giving them to every person you ever meet. It’s pretty much a numbers game (I compare it to fishing: the more lines you have in the water, the better your chances of snagging a fish). If you have friends that are in anyway connected to the same business (musicians, agents, pub owners, etc) force them to take a bunch of cards as well.
And of course, Social Everything! Facebook, Instagram, Snapchat, Twitter, Google+, LinkedIn etc…create separate business pages from your own personal page and post the heck out of it!
It’s a hard slog but remember that 99% of this type of “advertising” is all free. It’s all organic inbound marketing. It takes a while but you must keep at it.