We have gotten some tickets from players who can't find the Power-up Mag Ammo I. You need this in the "Gearing Up" mission.
To find it, go to the marketplace, and choose the Power-ups tab. From there, choose Tactics.
The Mag Ammo I can be found on the very first page of this area. Depending on your level, you will probably need to use the left scroll arrow to get to the first page.
We hope that this clears up the matter for you.
--The Mafia Wars 2 Support Team