If a message pops up in the tab there's something going on with his scepter when he does that just Defend! All of your might and gou need to keep om having high health because the attacks he does after the two scpeter magic beams he makes your health go to half with just smacks and tail wips of his to lower your health, when you see your low on health use bind and attack with all you got and remember to see a message when he is going to attack and defend immediately.. That's all i can say because i had my levels at 15 also and i struggled once but you'll get through that stage...

Up to your style . My style has weakness against immune flirt foe. You can upgrade your weapon ( I also did it) to reach maximum upgrade of your weapon . When you  fight with Selye try to combine Bind up skill with MP potion. Bind up skill is heal you more than HP potion. When you see left topscreen use defense.