If you craft just pistol ammo it will take you a while, this spreadsheet is very helpful for knowing what to craft next to level your firearms.
https://docs.google.com/spreadsheets/d/1Be69x7UBXwoowDtL1VaPJjBqwwPzQ0hzZOJwDMpMlPg/edit#gid=0
This thread by Sorle is very helpful...