Choosing the right mix of keywords can increase your reach while also reducing unnecessary ad spend. Google lets you set up to 20,000 target items (such as keywords or customer groups) per ad group, but you should be using less than 2,000 per ad group. The exact number to use depends on your business size, campaign goals, competition, budget, and keyword match types. Over your campaign's lifespan, you should remove keywords that fail to deliver results, test new ones, and continue to track keyword performance.