If it was me... I would do SEO and PPC ad network (not search network)... this way you get high ROI lol...(this is only if you want to make a lot of money and have a lot to invest).
I think you should spend 20% of your budget on PPC and 80% on SEO. I have used this technique and it worked for me.
I look upon SEO and PPC as being able to compliment each other. In the initial stages while SEO is being worked on PPC provides a short-term (though expensive) traffic solution. As natural rankings start to increase the PPC budget can be cut back. In the long-run though you can use PPC to pick-up the long-tail search phrases that provide cheap clicks and it isn't cost effective to SEO for.
I would like to recommend you to do SEO for your needful results and am sure it will bring the changes which you want....but u have to decide the thing yourself which is proper for you and your website.... Regards Puneet M