Any person who spends money with any business or salesperson will be influenced by the appearance of the business, and the same effect applies with your website design. All you need to do is make your site with an appropriate design and theme for your audience and follow good usability practices. Don't feel so all alone if you have been banging your head against the wall. You need to have webpages that evoke positive feelings and perform better, and we will show you how to do that.
If you really want to go all out with your on page SEO, then assign filenames the particular keyword that page is optimized for. The reason for this is, when search engines go through your website they look at the file names and search for any keywords that they could rank your site for. Your main keyword phrase for that page will go in the filename extension. Also, avoid using underscores when you do this and do use the hyphen. Doing this will allow your pages to be correctly categorized by the Google bot - since this is completely for the benefit of Google SEO. While this all by itself is nothing, really, but it will help your site with ranking ability and better listing in the right category by Google. Some of the sites that get a ton of traffic are very simple with their designs. But the final decision really depends on what your site will be about and what needs to be present. Be careful that you do not make it impossible to add anything in the future. One excellent practice is to draw pictures of your site so you can get a good idea of how it will look. Even when you're using ads, ensure that it doesn't look crowded, because that would only work against you. The bottom line is you have to make the call about your site design, not us - so we are just giving you suggestions.
Avoid going overboard with your design prowess to the detriment of properly displaying your content. A site that makes heavy use of Flash animation always makes us think the designer, or the webmaster, is just trying to impress people. If you want to use Flash, then you have to think about the purpose of the site and who your audience is.
Flash can slow a site down tremendously, so if you are not familiar with speed optimization you should be careful. If you really do want to use flash on your homepage, then make sure you have a link to an individual HTML page where your content is listed out. You should always think about usability when you are considering the use of Flash.
There are entire books written about website design, but you can discover enough so you can make your niche sites look quite nice. Most IM marketers can get by with just learning read more about some of the fundamentals of site design.