For a galleon, always try to have a LJ equipped if you can manage. The galleon is a broadside ship, so running all close range weapons will make you easy to kite when facing other long range ships like a sniper spire, lumberfish, or a front sniper side pyra. For rear guns, try running something defensive or a flare. Another tip for galleon is to watch out for carronade Fish. And the best way to counter these is to simply have your own carronade and each side and sink the goldfish with you.
My loadout I use is LJ, Carronde, Arti left for longrange capability and close range brawling, standard hwacha, carronade right side, and rear mine/flare depending on enemy load out.