Jiraiya takes this even though it will be a tough one.
Gaara's defense is incredible... but not inbeatable.
Jiraiya can summon Gamaken, Gamabunta or the other giant toad to aid him. He can use Swamp of the Underworld - How would gaara counter a Giant swamp appearing right under him in matter of seconds.... Gaara can fly on his sand.
Jiraiya got Fire - Earth release
Fire Release: He is very skilled and can shoot very powerful fire towards gaara.
Earth: Like his Swamp and more would do huge damage to gaara.
Now Jiraiya has tons of other jutsu, Toad jutsu which is highly dangerous in close combat... he can reverse summon him and his opponent into a toad stomach which immediately kills the opponent, or he can send him and his opponent into his barrier where he has the advantage. He has basically tons of jutsu to counter gaara.
Also he got shadow clones, toad silouet (can't spell) and hair needle jutsu to defend (hair won't do much against sand)
Then i believe he would get the time to enter Sage Mode, where Jiraiya will be incredible strong and fast.
His Sage Art is incredible: Senpou Goemon - A vast sea of boiling oil which would consume Gaara and his sand defense. Chou Oodoma Rasengan incredible Rasengan powers and Ma & Pa to aid him in battle with their Genjutsu or Ma & Pa could summon the 3 giant toads to the field and more.
I say Jiraiya takes this with high difficulty