The strategy to beating him with Sora is slightly different than Riku in a number of ways. For one, Slide Roll doesn't give you any invincibility unlike Dark Roll, so when he does his basic uppercut, you have to be out of its reach by the time it would hit you, or it won't save you. The same goes for his uppercut when it's empowered by lightning, which is nearly impossible to dodge with Sora. Thankfully, Sora gets access to Superglide, making it a lot easier to keep your distance from Julius when he's powered by lightning. The spirits were chosen for the magic boosts, magic haste and water boosts, since my entire deck consists of Magic commands. The reason I chose Unbound over Ultima however, is because the most common damage you'll do is still Physical, Counter Rush. Whenever he slams his fists together, get ready to block. Most of the time, the first 2 hits and hit 4 and up will go right past Sora's block, so when he does his combo, wait for the 3 strike to almost hit you, block, and counter rush right away. This way you completely avoid the rest of his combo and deal some decent damage.
Maybe i'll do Riku next after all. It's a lot easier with him thanks to Dark Barrier, Shadow Slide, Dark Roll and Doubleflight.