Is a sitemap important for sites that only has one basic page like index.php and all information at that page?
Actually no, i am talking about a very simple website with only one page with information or text, and possibly some adsense ads. In this case there is only an index page and nothing more, which is why im questioning the value of a sitemap.
then no a sipe map is not needed! Simply add the meta tags and content tags you should be fine! im not too experienced but maybe someone else can pass some advice on
No not required, it is required for websites/blogs with multiple pages or if you are planning to increase the no. of pages in future
Although a sitemap might be an overkill on a single page site, I still would recommend that you set up the Webmaster Tools account anyway. There is some good information about the site there.
I'm using the webmaster tools on other sites but I will try it at my smaller ones also, if it gets better then I will be a happy boy and if it doesn't then I have tried and failed and that's better than the other alternative Example of one page sites that I'm talking about? Just look at my signature and you will see two of them.