There are lots of App builder softwares are there. Just google "Mobile App builder for free". Many solutions provide a free version with limited features. Choose the best one depend on your need.
Most of the app builders are meant to create simple applications. They lag in many features compared to native code implementation( i.e Java for Android and ObjectiveC for iOS ). It is always recommended to go for native code, if your app idea is complex parts to integrate.
No matter which environment you use, you should know to code to build an application.
That is a minimum requirement. Even if you use no code to build an app, you could only make a modest app.
To build complex apps you should try your hand at coding.