As long as you're sure that no organic search traffic is coming in via ranked search results pages from your site, it would be of no harm just to prevent search engines from indexing those pages as per the robots.txt directive I mentioned above - then just focus all your attention on the other pages of your site.

With regards to the unique content, always try and find the time to produce unique content on the category pages, these were the ones you mentioned you wanted to rank. Normally this is feasible providing you haven't got over 1,000 categories.

Feel free to PM me over a link to your ecommerce website if you would like me to take a look at any of the situation in greater detail.

How I would handle this would depend upon the performance of the ecommerce website and which entrance paths via the website convert higher.

You could easily instruct search engines not to index the search results page by adding the following in your robots.txt:-

Disallow: /search.php?search=*

But is there a real likelihood of duplicate matching content with your actual category pages? It's unlikely in all honesty - but depending on your website content and product range, I suppose possible.

If many visits to your website arrive via indexed search result pages, I would be inclined to leave them indexed however and implement measures to ensure that they won't be flagged as duplicate content.

Ways to handle this depend on your ecommerce provider and it's capabilities sometimes but more often that not, is just a case of ensuring there is plenty of unique content on your category pages (as there should be) and there is no chance of other pages of your website hindering their ranking potential then.

The allow directives need to come before the disallow directives for the same directory/file paths. (I have never personally tested this although it makes logical sense to instruct a robot to access one particular path within a directory structure before it sees that it is blocked from crawling that directory).

For example:-

Allow: /profiles

Disallow: /s2/profiles/me

Allow: /s2/profiles

Allow: /s2/photos

Allow: /s2/static

Disallow: /s2

As per how Google have formatted their robots.txt.