First is your phone rooted?
Otherwise look here:
I have an other question for someone who knows more about this than I do:
When this phone (Galaxy S3 mini Value Edition i8200) is rooted, are you then able to install a custom recovery or even every custom recovery?
For exampel: twrp 2.7 or cwm 18.104.22.168 or PhilzRecovery or another ? Then you could also make a Nandroid backup.
I've searched for some info about this special Q but I looked at the wrong place I think, cause I didn't find any answer.
I know there is no custom ROM yet to install.
But in the meantime you can use Link2SD to move apps to the sd-card.
Hopefully someone is able to work on a custom ROM.