Create a GitHub deploy key in order to give your pipelines restricted access to just one project.
Learn how to store secrets / credentials in Jenkins.
An tutorial/example to get you started of using Jenkins for a CI/CD pipeline when you use GitLab flow.
Have a single set of "build" and "deploy" steps in your pipeline, but run different actions based on your environment.
Learn how to create a token that grants limited access to a specific project.
Generate a personal access token that will grant a service the ability to perform certain actions as if they were you.
Learn how to install packages hosted on a private Gitlab server using Composer and GitLab tokens. This is primarily useful for those setting up CI/CD pipelines with private PHP packages.
A simple CI/CD pipeline that will get you something simple/basic in place that you can the "build" (pun intended) upon. This way there isn't a steep learning curve.
A timestamped video walkthrough from "Davo'clock" on creating a CI/CD Pipeline to maintain and update AWS infrastructure with Terraform.