Be careful to use dual sim phone with Flexispy...I've rooted a Samsung J7 2017 dual sim and installed Flexispy and it works only in limited mode 1, not full. This is certainly related to the dual sim architecture of the phone. Bear in mind that in limited mode 1 you can't intercept phone calls, recording surrounding conversations, send hidden sms commands and more...
It's not a problem if you are interesting only in IM chats, SMS (only few persons still use them) or locations, or if you are not willing to buy the EXTREME version of Flexispy for economical reasons.
The procedure for rooting this model is quite simple to follow even without install a custom TPRW,
Take a look here: https://forum.xda-developers.com/galaxy-j7-2017/how-to/guide-how-to-root-sm-j730f-twrp-t3709597
You need also to install Titanium Backup app to remove SecurityLogAgent from the device, if not, an alert message will pop up on the phone very often.