Appindex have some great resource guides covering all aspects of app development. These are not specific to using app makers, but they still have some good information about things such as monetization and analytics.
Setting up your shop from scratch on an app can be a frustrating and time-consuming experience, but there are ecommerce solutions that most app makers cater for via integration, such as Shopify. If you’re interested in other ecommerce solutions you can check out the online comparison tool.
App Annie is not only great for checking your apps statistics after you publish, but also great for doing some research beforehand.
Google Analytics is not only used for web analytics, but can also be used for your apps. The majority of app makers allow integration with Google Analytics, as well as often having their own analytics system. You can also use their Keyword Planner to help in preparing the best keywords to use within your app marketing and in the store.
Top App Charts is another site you can use to check the rankings of apps within each category and app market. This is another one that’s good to use for research before, and after, you publish your app.
Sensor Tower is another great ASO resource, similar to App Annie, providing information about stores as well as individual app data. They also have a great blog that contains a bunch of helpful information for beginners, to advanced users.
AppMind is also another site you can do to help get some keyword ideas.