You have to be very careful using idiom list only use reputed material such as PR or
manhattan GMAT.
Manhattan GMAT is good one.
Particularly, be very careful with prepositional idioms. Lot of lists on web contains widely used prepositional phrases but their may be some obscure use which may be ignored for ex. ‘centers on’ is correct so does ‘centers upon’! Some of list will include only one of these idioms not both.
So if you cram, use only Manhattan or PR. use everything else as a standard usage but not the only use.
More over be smart about how to use idiom list.
Neither … nor-- yes this is idiom so if you see neither…. or it’s wrong. But ‘neither’ can also be used as subject of a sentence.
Not only… but also is idiom and if you see one without another it’s an error.