which one is better source of traffic?

Find exactly what source of traffic is working for you at this time to give the sale. If you are getting any traffic at all, it is necessary to find the source of work and it is not.

Once you know what the source is currently working, all the others and cut a considerable emphasis on that brings you money!

Use your major competitors such as search for what they do and then just do a better job of it. Do not reinvent the wheel in traffic in your market. If you see that bigger players have to pay for clicks of thousands of keywords, you know it works!

So will do it and do a better job on them and then you make more money.

Begin to sell more expensive services if you can afford to buy more traffic. Because almost always the most expensive traffic is often the best and you can get more of it.

If you can double the amount you spend on AdWords, you can probably triple the amount of traffic you get to go after the keywords that work best for you. This is a great way to massively increase the amount of qualified traffic that comes to your site.

The best source of traffic is the one who fits you. The people are different. Choose the sources of traffic you are comfortable with.

If you have money to invest, then outsource what you can't do or you don't like to do. In this case, your question is valid. You have to find the optimum balance between expenses and profit.

The best source isn't necessarily the source that sends the most traffic. The best source is the best targeted. I'd take a hundred highly targeted visitors over 1000 random visitors any day. The best source for YOUR PURPOSES depends on where you can most effectively target the right audience.

It's different for everyone as it depends on your skillset. For me, the department where I'm pretty good at is organic listings aka seo. As a general idea I like paid traffic much more. Although as the name says, you have to pay - it is instant. It doesn't take weeks or months.

But since free works better from a ROI perspective this is where I'm currently concentrating my efforts.

Zoobs - I've found email marketing (with the exception of your own list) to be very random if you're renting a list etc - despite what the owners of the list would tell you...so for highly targeted traffic social media combined with less competitive, targeted keywords wins hands down.

Email marketing for an opt in list is hard to beat.

After that I'd put organic search engine traffic.

Then affiliate traffic.....after that the quality falls off a cliff and ends at articles, then social bookmarks etc etc.