The present disclosure is related to managing delivery of items of invitational content based on a feature-based model. Specifically, a content delivery system is provided for managing a campaign using a content bundle identifying different content blocks and rules for assembling the content blocks into the items of invitational content. The feature-based model then accrues costs based on content blocks delivered, content blocks accessed, a degree of user interaction with the accessed content blocks, or any combinations thereof. The relative performance of the items can be evaluated by obtaining a ranking based at least on the number of content blocks and a performance of these content blocks. The ranking can then be used to manage future assembly and delivery of items. In some configurations, rules can be provided to specify when particular content items can be included as costs vary.