Note : We recommend saving upgrading anything until you have a much larger swathe of components to choose from. That way, upgrading is much more efficient and cost effective. You shouldn’t even need to upgrade until around Chapter 10 because you won’t be running into anything that should cause you too much trouble and the game provides enough Crystarium upgrades to keep up.
Remove Doctor’s Code and any other accessories you may need from Sazh if you wish. The party changes again after the cutscene to Lightning and Hope fighting off a group of Corps Gunners and a PSICOM Tracker. It is likely you will need to use the Double Dose Paradigm for super fast healing because they can decimate your HP quickly. War and Peace can also be used to maintain the Chain Gauges of your enemies so should be created if you haven’t already.
Spend any CP you have acquired - work towards Accessory (Medic) and Launch (Commando) for Lightning and then upgrade the Ravager role first, Synergist (which has an Accessory crystal) and finally Medic for Hope.