Not spend much money on marketing... or do you want to make money?
Free methods or low cost methods generally don't work.. (otherwise why would anyone do the paid methods right?)
So you are interpreting the entire purpose of marketing completely wrong.
You need to do your cost/deal calculations.
What you are doing is wrong. You are just focusing on spending little money but you are not looking into effectiveness of the marketing method.
Sure DMM is super cheap if you send out 3 mailers. But how effective is it?
Find the cost/deal for each marketing strategy, and then weigh in the amount of work it takes and choose. Don't go by how cheap it is. Go buy how effective the marketing is.
If you want the cheapest way (free) yet the most effective way... that is SEO.