There seems to be some confusion at the moment as to whether Dragon Ball FighterZ has loot boxes which you can spend real money on. Let me tell you right now: it doesn't.
Or at least not right now, anyway. Who knows what the future holds for the game, but when it launches on Friday there'll be no way to spend real money to unlock items such as character colours, titles and lobby characters. They have to be unlocked by actually playing the game.
Pretty much everything you do in Dragon Ball FighterZ rewards you with Zeni. Completing the first arc of the story mode, for example, rewards you with 50,000 Zeni, while completing a single combo challenge rewards you with 500. As such, you accumulate it pretty fast.
In just over 10 hours with the game I'd nurtured a nest egg of around 200,000 Zeni, and what is it used for? Buying Z Capsules.
Now, admittedly, Z Capsules are loot boxes. You can't currently buy them with real money though, only Zeni. One capsule is 1,000 Zeni, but you can buy them in bundles of 10 for 10,000 to save time if you wish. Each capsule contains one random cosmetic item, but if the item you get is a duplicate, it's changed for a Premium Z Coin instead. 10 Premium Z Coins can be used to buy a premium Z Capsule, guaranteed to give you an item that you don't already have. And yet again, 10 premium Z Capsules can be bought at once to save you time.
Overall it's quite a painless process, and you can have a majority of Dragon Ball FighterZ's content unlocked with very little hassle. So if you're worrying about paid loot boxes being in Dragon Ball FighterZ, don't.