The problem with employing outside agents is that you never really know what you are getting for your money. Ultimately, SEO will always depend upon what your competitors are doing which always leaves the door open for the amount of work and the price to keep going up, even though you don't understand why.
SEO is here to stay, if you don't understand it now, and you want to survive into the future, you are going to have to get to grips with it at some point in the future, so the sooner you start the better.
There's heaps on the internet to research, here's some general topics to get your head around.
Learn about directory submissions. This is not a pretty way to build inbound links to your website, but you can do it in numbers and it works. The more inbound links you can get, the better your website will rank.
Learn how to write and submit articles. Article marketing is an excellent way to build search engine positions. You write an article on your topic and place it on an article site on the internet, generating a high quality inbound link in the process.
Learn about news and press releases. Rather like articles, news and press release sites allow you to post article on your topic and gain links back to your site.
Place new content on your own website regularly. Google likes web sites with more and more content on. News articles are ideal for this. If you don't have a website where you can add content such as news it may be worth getting one.
Don't be afraid to ask your clients for a link off their website. It may be hit and miss, but their websites will be highly relevant and so excellent quality links...they can only say no!
I do believe into the future, recruitment agencies who develop their own site's presence on the internet now will win in years to come. Contracting SEO in is a troublesome at which you could loose a lot of money and not get the desired outcome. After years of trying various companies I decided the only way was to learn it myself. It's not a complicated area and it may save you a lot of time and money. Research these techniques above on the internet and you will soon be seeing results which could both make and save you money.