First in my list is the Support , if this cannot be handling the cases and issues by players then this is a BS site.
Second on my list is the Withdrawal fees , Im sure many of us will favor here because like us who is small players we are always seeking for shorter fees.
Third on my list is the Advertising , this is one of the most important for me because this shows how capable the site to handle business by spending funds for them to lure players.
costumer support is important but I do not prioritize this because luckily I have been gambling for years and not experienced any major problems. There are small problems but I can troubleshoot them myself and there is no need to call for the support.
When it comes to withdrawal fees you can choose altcoins when you deposit because withdrawal fees for altcoins are usually tiny compare to when your gambling with bitcoin. For the advertising part, not really because there are shady casinos that are continuously been advertised inside and outside the forum and there are also casinos that are legit but do not do frequent advertisement.