What campaign type and Smart idding strategy should an advertiser set up in a Google Ads campaign in order to show ads across YouTube, Discover and Gmail feeds to get as many sales as possible within a set budget?

Discovery campaigns are specifically designed to show ads across YouTube, Discover, and Gmail feeds, making them the ideal choice for reaching users in these environments. Maximize conversions is the appropriate Smart Bidding strategy when the primary goal is to get as many sales (conversions) as possible within a set budget. Shopping campaigns are for product listings, not for ads across these feeds. Sales and Target ROAS (Return On Ad Spend) is a good strategy for maximizing revenue, but Discovery campaigns are the correct type. Maximize conversion value would optimize for the total value of conversions, which might not necessarily lead to the highest number of sales if some sales have lower value.