Neptune shows what deprives from you in your life. For example, a person with Neptune on the 4th on the natal astrology chart will probably have issues with having no home: being in institutes or in jail. A person with same Neptune but on the 9th may show, depending on other planets involved, a lack of efficient supporting system that allows either publication of the individual’s creative and/or personal materials or going through high education – as well as any other 9th house related topics. Not only Neptune shows what lacks, is missing and deprives from your life, it also tells us in what way it does that or how it happens. Neptune on the 3rd – means of communication are being deprived. May indicate an “on the spectrum” behavior or having little or no siblings, neighbors and everyday attachments.
Neptune on the 2nd – personal assets are being deprived. Popular in twins charts, when they are born into reality of sharing everything they have (from placenta or womb to parents and family, sometimes friends and school)
Neptune on the 1st – Sense of self is being deprived. I believe these people tend to have narcissist relationships as a result, sometimes.