Use social media to market your business (it’s free). Also joining a networking group (especially one with other small business owners) would be my next choice. Or you can donate $50 of your services to a local fundraising event as part of a silent auction.
Social media is the big ticket here just as a few have mentioned above. Don’t forget about making and posting your own Youtube videos. They come in handy in your social media campaigns but Google loves them and will index them all over the place. Good luck!
I had just slightly less than this when I first started on my own. I purchased website hosting and T-shirts with the web addy on them. These went out to EVERYONE I could get to wear one. Had an added benefit of brand recognition as well.
With todays online marketing tools, a nice website can be built and maintained with a $50 budget. Couple this with free social media sites such as Facebook and you will be able to reach a lot of people!