What is the best practice to create application?

It's hard to answer for sure without knowing your use case, but here's some general guidance:

• I've found Quick Apps most useful when creating a simple application. For example, a good use case is if you want to replace a spreadsheet with a basic application where you can insert / update data. Quick Apps are also useful for creating templates / demos or planning out how what data you want for your application.
• Creating an app from scratch is useful if you want to create a complex app or if you have very specific requirements. It's also generally useful for developers who have more experience.
• There is also a third option. If you create in the Appian Designer, it gives you an option called "Create Using Application Builder (Basic)". This option goes through the same wizard as you see in the quick apps designer. However, it creates fewer objects and uses a simpler data structure.

If you are new to Appian and want to figure out the best way to start, I'd recommend the third option. It will create several objects for you so you can understand how everything fits together. However, it still keeps a simple application so it is easy to change.

If you're still unsure which one to use, let us know what your use case is and we can also provide some additional suggestions. No matter what you choose, I highly recommend also viewing Appian Academy to find more information about how Appian works and how to create different kinds of applications.