I have the same party as you: Lightning/Fang/Hope. It's a pretty win combo if you ask me.

The Official FFXIII Guide says the best strategy to complete the game 100% is to do this: From about Chapter 6 onwards, don't spend any of Snow's/Vanille's/Sazh's CP. Instead, save it all up so that you have at least 700,000 later on to spend making them 'Super Specialists' (focusing on one single role each). Keep your main party as Lighting/Fang/Hope all the time and only use CP in their 3 main roles.