Who is your customer and what are you providing for them? If your customer is the job advertiser then do they want fewer to apply, more to apply, or the best to apply? If your customer is the job applicant then how are you saving them time or reducing risk?

I like that you are focusing on the common sense aspects, if you get the basics right then I think you will be off to a good start.

A good initial start for your site would be to standardize the amount and type of information for each job advertisement so that applicants have an easier time comparing them.