Internal Links significance

Internal links are the links to other pages in the same website, mostly your own web site.
From your first , home page, provide links to almost all the pages, so that your site will be searched properly by search engine. But in practice i found no special advantage from this. The search engine is not searching all the links provided in the first page.
But one advantage we got. The traffic visit all the pages or maximum number of pages and thus it resulted in maximum clicks generating more ad revenue.
The theory says that a web page should not have more than 50 links. So, you restrict your links to 30 or so, as unknown links provided secretely by the web site, ads, counters occupy the rest of 15 links. A web page should have minimum 200 words to maximum 600 words. This is also not true. I found some pages with less than 200 words ranked by google as PR1 for no specific matter in that nor links exchanged.
reciprocal link exchange programs (like linkmarket.net) are not found very useful. But they help us in some way. the content through their links are read by the ad engines and provide some variety ads, which may bring costly ads to your site.