Work on artifacts (purple and gold ones), upgrade passive familiar skills (some of them give 10% infantry attack for example), spend all of your guild coins on jewel chests. I am getting over 100% mix stats just from jewels. Finish vergeway, you get 11% mix attack and 20% hp/defense from it. And the last one is pretty obvious but make sure you are in war/mix talents.
How to get stats up even with gear I am not up to 300
Work on artifacts (purple and gold ones), upgrade passive familiar skills (some of them give 10% infantry attack for example), spend all of your guild coins on jewel chests. I am getting over 100% mix stats just from jewels. Finish vergeway, you get 11% mix attack and 20% hp/defense from it. And the last one is pretty obvious but make sure you are in war/mix talents.