An advertiser should group their campaigns by:
type of product or service
number of keywords
maximum cost-per-click (CPC) bids
number of ad groups per campaign
Explanation:
Organizing your account allows you to better serve the right ads to the right customers, and it allows you to better track the effectiveness of your advertising efforts. When you need to use a different set of campaigns settings (ex: budget or location targeting), create a separate campaign. For instance, if you sell clothing, you may want to set a budget for shirts and a different budget for pants. In this case, you should create a campaign for shirts, and another campaign for pants.
A good rule of thumb for creating an effective campaign structure is to mirror your website’s structure. By creating campaigns and ad groups around a specific theme or product, you can create keyword lists that directly relate to the corresponding ad text, and ads that link directly to that product’s page on your website. You can even add keyword-specific URLs to improve the quality and relevance of your ads in your account.
Read more here: https://support.google.com/adwords/answer/2375470?hl=en
