It would be too expensive around here to hire an agency. I do most of my own marketing. Maybe taking some classes would help you with your branding skills? I hope you find a solution soon.
I've hired an agency before. I honestly wasn't impressed. I was new to the field though, and didn't know what to look for. Definitely do some vetting before you sign the contract.
You can choose to rely on platforms where there will be clients waiting, but you'll have to make a decent portfolio even there. I don't think hiring an agency would be the best choice when you're only starting. It'll be a loss if you pay for it and get no clients in return.
Oh! Tough market! I don't live in CA, but I know the competition there is pretty high. If you can afford it, why not? I think advertising your business is an excellent way to attract potential customers quickly.