It's really difficult to give a list of must have or recommended apps as everyone uses their devices differently, have different priorities, already have accounts with various services and want the app for that service etc... etc....
Having said that for me the following are installed on all my devices (both rooted and unrooted).
Launcher: The Stock launcher is quite limited in terms of customisation (both in terms of aesthetics and usability) and is a little buggy on the Moto G. I use Apex Pro as an alternative - Nova Prime is similar and a favourite of many and there are several other good third party launchers.
File Explorer: Useful for moving file around the device, housekeeping etc. The best allow you to access shared folders on your PC or other Android Devices on a wireless LAN, integrate with Cloud storage providers and can stream media from Cloud/LAN storage. I never need to physically connect my devices to my PC to move media around. Again there are a number of options but my preferred is ES Explorer. FX is good as-well with it's sister app Websharing, but it's media streaming options are a bit limited compared to ES Explorer.
Battery Utility: There will be times when you want some more detailed info about battery usage than the basic OS can give. There are thousands of Battery Utilities on the playstore, many with very specific uses, and many of which are pretty useless. As a genuinely useful general Battery Utility I like GSAM Battery Monitor.
Email: The stock email app is also a bit buggy on Kitkat (it's not compatible with my ISP email service for example). If you have issues K-9 Mail is a good alternative.
Other than that everything is probably down to personal preference, how tied in you want to be to Google Play for books / movies / music and what you are mainly using your device for. Many folk go for third party music, video players, e-readers, messaging services, RSS aggregators and browsers (my preferences are PowerAmp for locally stored music, MX Player for video (local or streamed), Aldiko for reading and Firefox as a browser).
Automation apps are not for beginners but once you know your device / Android reasonably well can make your 'smart' phone into a genius. Tasker is the most famous. I like MacroDroid.