How to replenish gadget ammo in Marvel's Spider-Man
Gadgets are a necessary part of Spider-Man. They give you the tools to clear out enemies a lot quicker than your basic punches and kicks ever could.
You're limited in the amount of gadgets you can use per battle, however, due to the ammunition system. This forces you to be conservative with your gadgets and only use them at the best times.
Sadly, there's no automatic way to replenish your gadget ammo. You can't buy ammo stock, either, so you'll be forced to do some specific actions in order to restock your arsenal.
When your Focus Bar is full, you can perform a finisher by pressing the Triangle and Circle button at the same time. While this offers a quick kill to an annoying foe, it also provides you with one random gadget refill.
Get specific Suit Mods
A late-game Suit Mod known as "Metabolic Converter" gives you the chance to generate gadget refills when taking damage, giving you an extra way to get back on your feet. There's also a "Scavenger" Mod, which gives you bonus gadget refills for finishers.
Most of the time, you might just be forced to wait in-game for your gadgets to replenish. Each one is on an invisible timer and they'll gradually restock in between missions and fights.