Threshold for MATK% and Int%?

I've long since wondered when it is appropriate to begin to prioritize MATK% over Int%, or even vice versa. Obviously, it would be ideal to stack both, but I'm not in a position with Spina nor BS'ing to be able to accomplish that just yet.

 

Depends for finale it scale with int with tier 5 I hope they wont fuck mages again

 

For the rule of thumb, always add 1%MATK for each 3%INT. Ideally, you would want it to be balanced, since adding INT alone or MATK alone wouldn't even compare to adding it both with the right proportion. You might be asking why, but let me explain. Adding INT% means adding raw MATK to your stat. This raw MATK will then be multiplied further by MATK%, making your MATK grow more than simply adding MATK alone or INT alone.
Though there is only a handful of xtall/add that could give a meaningful amount of INT%, and there's a lot much more worthy MATK xtall. So, I recommend stacking INT% from crafted gear only.

EDIT:
This is considering you only pursuing raw amount of MATK. As a mage, you need to consider many different things such as CSPD, crit, and cdmg, if you want to build your mage as so. Just try to look at youtube for reference, maybe you will get some new idea for your build.