nubai: The JP wiki section with 2C combos is here: 2C FC combos. As for 5CFC because of distance sometimes it may not even be possible but you will generally need to adjust with a superjump or normaljump, extra JA's, or use a B dive on the first rep.
DP bait: yeah abyss is right, crossup setups in general will be your DP bait.. and like you said it tends to get obvious if your always doing 3a>214C.. so you have to mix it up alittle such as...3b(6a)>214C, 6a>214c, and some 3c variations like 3b(6a5d)>3c which tends to be your corner bait option.
ragna: yeah ragna's a hard matchup.. in general you want to be in situations where they dont' get up into 3a>3a pressure after going into curse. You want to go straight into a blocked D bug high/low gimmick after a JA>JC>JD or corner 5a>6b>j6d