I have not advertised at all - I don't even have any business cards - since forming my business in 2007. This is heavy part-time for me, though, and a I am not trying to grow, but I have every year. I do have a web site but it is mostly to send someone who has found a way to contact me.
However, I owned a retail music business for ten years and bought hundreds of radio ads. I can honestly say not one of them ever paid for itself. Over the long haul, as a part of our overall marketing, radio ads had some value with regard to maintaining a presence in the minds of customers and potential customers. Trade deals with radio can be worthwhile IMHO. We found newspaper advertising worked better and was remembered longer. The standard argument then was people do not pay to receive radio programming so they attach less value to it and jump around from station to station a lot (often when an ad comes on). People paid for newspapers and had to put some effort into using (reading) them. That was before the Internet. Now I suspect there are as many distractions for print as there are for radio and TV. Cable TV was very cheap at the time and sometimes worthwhile, but then again we were in the entertainment business. Or best results by far came from direct mail with existing customers. We had a good customer tracking software package and knew hundreds of our customers personally. That enabled us to tailor offers well and pick and choose who we mailed to. If we had an idea and a need for a spike in business we could put something together one weekend and have it in the customers mailbox the following Thursday and see a percentage of them that Fri-Sat-Sun. Sometimes we would do a thank you type offer to as few as 25 customers who had been frequent buyers. Other times we would select 1,000 customers who had purchased 20 or more CDs from us who we had not seen in 6 months. Things have changed so much. It used to be that water was free and people paid for music. Now it's the other way around.
I can't say what would work now but I would be cautious about buying radio ads. At least once a week I hear a series of radio ads for some new business and I know two things instantly: there is no way their gross sales are going to cover the cost of their radio ads that week much less have their gross margin cover the expense & they ain't gonna be around in a year, probably due in large part to what they were talked into spending on radio.