After being busy with other games and with Cross coming out really soon, I came back to MH4G and my sub-file and cleared the final Village quest as well as unlock the G-special class SOLO. That's the big point. On my first playthrough, I did the G-special class unlocking in a party and did the final Village quest later on. Now without the best equipment possible and people to help me, it really feels like I have reached the goal by myself.
Oh, BTW, this sub-file is a Charge Blade-only file.
Before fighting Gogmagios, I wanted to be as prepared as possible, so I decided to go ahead and do the final Village quest first in order to Extreme Forge my weapon.
I decided to use the Teostra Charge Blade for the obvious reason that Deviljho and Diablos are both weak against Blast. And... Seregios is just weak. I actually had a hard time when I first played the game and this quest, but now that I have had so much experience fighting these monsters, it was actually quite easy.
And yes, I did die once against Jho.
After beating the final Village quest twice to get the materials needed, I extreme forged +Defense onto the Rathalos Charge Axe. Of course, the one that uses the Gold and Silver materials.
I chose this Charge Axe because Gogmagios starts off most weak against Fire. He later becomes more weak to Dragon, but his body gets liquidy and soft permanently at that time, so there is a trade-off. So Fire is in general, better at handling Gogmagios throughout the fight.
I increased my defense past 700, increased my Fire resistance past 20, and gave myself immunity to becoming entangled by the oil, so I would be able to survive and avoid all attacks, avoid all accidents.
As a result, managed to defeat him with time to spare. He still did some heavy damage (especially his body slam), but nothing to kill me with. The Fire resistance really helped in avoiding getting burned by his later exploding oil puddles, and I did get hit twice with his laser explosion.
Anyways, finally did all of this solo and am happy and ready to move on.