I have a $10 Walmart LG smartphone. There was about 250MB of free space on the internal memory. I went through and disabled (click disable button on each app) most of the preinstalled Google aps ( cloud print, drive, google play books, google play games, google play movies and tv, google play music, google play newstand, google search, google+, google maps, youtube, google text to speech engine). All of these apps are not useful to me. Now there is 1GB of free space. I also don't get the constant and very annoying auto updating ( which slows down the android device), especially when trying to download something. I have an app called TuneIn Radio pro ver 7.1 that I installed myself. This program records radio stations that are playing on the android device. Depending on the bit rate of the radio station, (for example, high bit rate 250kbps) can use up 120MB per hour of internal memory. Now with 1GB of free space, I can record about 8 hours of music before the internal memory is full. Once I have recorded the file, I can later move the file to the external memory (sd card).
TuneIn pro ver7.1 does not allow you to record directly to the sd card.
So, in sum, I would say that you should disable all the pre-installed apps that you don't want. This will free up quite a bit of internal memory.