actually if your not in a hurry i wouldnt say grind red scrips for the books.. just do the custom deliveries, it will take a couple months to get all the books but the effort is minimal.

that being said if your using collectables to level your other jobs then you will have a lot of red scrips avaiable to you in time. and you could use them to help stockpile materia for when you can finally overmeld.

also if your not levelling quickly i wouldnt worry about overmelds at all til you have all jobs at 70. focus on supplying mats to the market that you can easily make and youll start to earn gil for the next patch cycle and then you might be in a better place to utilise the melds.