Though fighting the Ivory Lagiacrus is extremely simple, to me at least, I'd take Tomberdepp's advice and use the quests he recommended instead of the DLC.
If you were asking for tips on fighting the Ivory Lagiacrus, it depends on the weapon you're using.
If you use the Dual Swords, like I do, I stay directly in front of it and continuously attack it's chest area, right under it's neck. It is a known weak spot and is a pretty good blind spot.
When it decides to do it turning tailwip, dodge in the direction it's turning the you won't get touched but be dragged by it's body instead, dealing you no damage. I manage to kill G-Rank Ivory Lagiacrus in a good 5 minutes every time.
Attacking its tail is another alternate way to secure an easy victory without having to deal with much difficulty. It's easy to read when it will swipe with its tail if you keep the camera where you can see its head. When it turns its head around to look behind it, it will swipe its tail. It is easy to avoid.
Ivory Lagiacrus is my favorite Lagiacrus because it doesn't go underwater. I despise underwater monsters with a passion.