Once you have done your initial optimization you can over tweak and analyzing.
From my experience having page rank (by getting backlinks) helps with the more difficult to rank for keywords, for exampe if you are floris competitive keywords are " send flowers" . Getting backlinks with those keywords in anchor text will help ( hint try an use 2 sets of keywords in your title/ anchor text like " Online Florist- Send Flowers Worldwide "
You might get 20% of your traffic from the sought after terms terms "send flowers" or "online florist" if you rank well in search results.
You will also get about 80% of your traffic for other terms you have never even heard of or are less competitive strings ; i.e. " send thanksgiving flowers, order white Christmas arrangements, Oregon funeral flowers, and so on.
I cannot recommend highly enough adding new content. Without a doubt the best way to do this is with a CMS or blog. Blog can be used as a "news source" for your product or service an not necessarily as a journal- think of it as an easy search engine friendly way t publish content, . Every post will contain potential strings of keywords. Every post will give your other pages more " weight" and credibility. A site with 5 pages about flowers vs. site with 500 pages about flowers.
The best way to get higher rankings and more traffic almost instantly over optimizing your site is to install a blog and post content at least 2-3 times a week.