Is it laxus strong enough to fight gildarts?

Yes he is.... he beat all five members of RavenTail who are meant to be the anti-fairy tail guild elites..... he beat Natsu in one hit in their rematch when Gildarts fought Natsu in the Tenroujima arc and had to use magic... he fought (in the fighting ) he fought Mystogan, Erza, Natsu and then Gajeel with Natsu and fought evenly until he used fairy law

totally!!hades remarks he is strong enough

Yes CHOCOLATE

If he really put his mind to it, I'm sure he could. The magic council was thinking about making him a wizard saint, but decided against it because of his "boorish behavior".