Kisame and Suigetsu. Kisame has an advantage against Gaara and Suigetsu can't be hurt by physical attacks. Suigetsu and Kisame are a good team. Not only Kisame can use big water masses, Suigetsu himself can control them. Since Kimimaro uses physical attacks only, he's no danger for Suigetsu. For Kisame and his water masses Kimimaro and Gaaras Sand are also harmless.
So I say Kisame and Suigetsu with low difficult.