The built in Camera app is as easy as it gets.
Other apps may add more features, and possibly some more controls, but they are no easier.
As far as Good pictures, the camera itself is fairly limited. Its primary purpose is for video, and it is ok for that, but it has an extremely low resolution (less than 1 megapixel) compared to most modern digital cameras. No app can correct that. It's hardware.
The best way to get better pictures is to have good lighting. Nothing else is going to make much of a difference.