The long, straight path would be: do dailies for full 66s, then go into HM flashpoints to get full 69s. Then you can do story mode SNV/TFB for set bonus 69s. Then you can do HM SNV/TFB for full set bonus 72s. Then do NIM TFB/SNV for full 75s. Then do HM DF/DP for full 78s.
If you want to save some time you can do TFB/SNV HM in level 63 gear. You can also do HM DF/DP in mixed 69/72 gear.
This is precisely how the game seems to be designed. Though you can really skip the NiM content and use commendations to get Oriconian 78's and that will get you through DF and DP.