Ratix isn’t even mentioned in SO2, unfortunately. There are a few references to the game here and there, but each Star Ocean is designed so that the SO newbie won’t have to worry about missing anything if he or she missed an earlier installment of the series.
Anyways, you’re right about Orchestra. It increases your chances of item creation success greatly, but unfortunately, it’s not available until Disc 2. However, I can assure you of one thing: there’s only one skill that you will use extensively on Disc 1, and that is Pickpocketing. Aside from making valuables with Metalwork and selling them, that is.
Make sure your lead character has the Dexterity talent and build up his Pickpocketing skill (Poker Face, Courage), and start Pickpocketing once your level is quite high. However, make sure that when you’re done with Pickpocketing, you work towards getting the Orchestra and Blacksmith super specialty skills for Disc 2.
The most important skill to max out first for ANY character is Perserverance. This reduces the SP cost of all other skills.
Finally, for Claude, begin with Perserverance (of course), then work your way towards boosting his attack power through Kitchen Knife. Poker Face and Danger Sense are important as well for boosting Guts and Stamina respectively (with more Stamina, your HP and MP recover by greater amounts after battle). Good battle skills to invest in include Spirit Force, Below The Belt, Gale, Mental Training and Feint. As for Killer Moves, begin by using the Head Splitter attack, then move on to Burst Knuckle, Ripper Blast, Twin Slash, and then finally Dragon Howl and Mirror Slice.
So, that’s about it, I suppose. Like I said, go for Pickpocket in the beginning (and give it to Claude since he’s your main character and thus can pickpocket during Private Actions and during a certain scene in Disc 1). Once you reach Disc 2, item creation becomes a bit more accessable and fun.