How much Ammo should I use to make it a worthwhile practice?

with a Bi-Weekly / Twice a Month Trip to the Range routine, How much Ammo usage would you guys suggest to be a worthwhile practice? I feel like shooting "as many rounds as you can" isn't a good way of pratice or financially feasible.I would like equal practice for my two 9mm. Would you say 50 Rounds per gun is too little? via /r/CCW https://ift.tt/8Ad7zOV