I figure that Boboiboy would be using his second tier elements rather than the first, since he'd be 7-B otherwise. Even when he's 7-A in dura like that, his damage is still not going to phase Gildedguy. Anyways...
As Psycho said, GG can passively amp himself throughout the entire battle, and said amp can accelerate when he's in a losing position. It's still a major problem in this battle overall, regardless of what state GG is in. His armor can also withstand fire and heat, so fire and blaze BBB are out of the picture. That leaves the other 5 elements (I assume Solar is restricted due to being too high of a tier). Which part of OG series is this Boboiboy again? The series one or the movie one?
What are the specific elements/attacks that allow BBB to have planetary range attacks? Due to SBA, both combatants will be starting 4km away from each other. GG can extend his sword to several kilometers, so he should also be good in the range game thanks to the distance.
As for the specific elements, lightning is Gildedguy's main ticket to victory, while Cyclone is the one that bring the most danger to him normally.
For his lightning absorption, he can also redirect it back at the other BBBs and/or trick him/them to keep using lightning on him or something. Eventually GG may be able to absorb a potent lightning attack and amp up tremendously from that. Otherwise he can just amp immediately right from the get-go. BBB going Lightning Speed on GG would be a big death sentence for the kid, because he'd be entirely absorbed into GG, and it'd be a GG for GG.
Quake is big hands, and summons. It might not be too much of a problem for GG, but I'm not sure.
Thorns would be useless due to the LS diff.
Blaze is also likely useless unless he's going for the meteor attack, which can be especially concerning when paired with the ice eruption thing.
Ice BBB is a problem for GG, especially with the danmaku and freeze attack.
If Boboiboy lands a cyclone drill on GG (I assume that's where the dura neg comes from, based on the particular scan), then it's the end for Gildedguy, period. Otherwise, Cyclone seems very defense and mobile rather than full-on offensive.
The one game-changer that Gildedguy has (depending on how it's used in canon) is the stella-pen. On paper, Gildedguy can just enchant himself to be resistant to all of BBB's elements, reshape any of his attacks into whatever he wants, or even spawn anything he wants from thin air to aid him in battle. In a real fight? Not sure. Need someone knowledgeable to fact-check me at the moment. (I'll be going ahead and watch his vids now or something).