Well, you will need to be running Android "Marshmallow" to be able to run apps from the SD card. It allows this because it will turn the SD card into "Internal" storage rather than the standard "External" storage. That is if the manufacturer hasn't limited that option.
Now on that phone you should also be able to have up to a 32GB SD card, if you are running "Marshmallow" and the option isn't restricted, having a card that size would give you that much space for apps, etc.
How to turn external SD card into internal storage on "Marshmallow".
NOTE: Please be sure you start with a blank SD card. It needs to be blank because when the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device).
1. Go to device “Settings”, then select “Storage”.
2. Select your "SD Card", then tap the “three-dot menu“ (top-right), now select “Settings” from in there.
3. Now select “Format as internal”, and then “Erase & Format”.
4. Your SD Card will now be formatted as internal storage.
5. Reboot your phone.
NOTE: If you don't reboot the phone, many things may not work correctly, so make sure you do.