Advanced Custom Fields (ACF) is the most popular plugin on WordPress to make Custom Fields. That is because it’s so easy to use and most of their features are free.

• Their interface is really well designed and therefor easy to use.
• They also allow you to create Custom Post Types now, which removes the need for an extra plugin.
• They have a pro version that allows you to create galleries, repeater fields and option pages. But for the money you can better get JetEngine from Crocoblock.