Investors will surely want to see what you have in place after reading your whitepaper or seen your ICO promotion. Therefore, the need for a website for a startup is very important. To look more official, you may consider an appropriate extension for your domain such as .io, .ly instead of the common .com extension.
On the website, create a landing page specifically dedicated for to the crowd sale.
In a 2015 B2B lead generation report, marketers (ICO marketers included) are more focused on achieving a quality lead than quantity. Of what use is lots of interested investors of which only a few eventually invest? Lesser with higher conversion is better.