Final answer:
Choose the pay-as-you-go pricing model for OCI services to avoid upfront costs and to be billed based on actual usage, suited for applications with irregular usage patterns.
Step-by-step explanation:
If you are looking to use Oracle Cloud Infrastructure (OCI) services for application development with a flexible cost structure, the pricing model you should choose is the pay-as-you-go pricing model. This model allows you to pay only for the services that you use, without any upfront costs, offering billing on an hourly or monthly basis depending on your consumption. This flexibility can be particularly advantageous for projects with irregular usage patterns, as it aligns costs directly with your actual service consumption.