Why did I have to leave 20 boxing this story event to the very last day... I hope I get a ton of crystals from the golden gifts.
Every time Granblue Fantasy releases a new story banner, it gives you something called a draw box to pull from. You get an in game currency called tokens which drop from raids, and you use two tokens a pop to get a random item until the box is empty, and then you reset it. Depending on what number box you're pulling from (You go from box one to two and so on, in sequence), there are different sets of items. You can also draw in bulk, and pull a full box after box #4 if you have the tokens to do so.
Most of these items are totally worthless unless you just started yesterday or something. There are tons of them, about one thousand something, and each box takes 2112 or 2114 tokens to fully pull from, except for the earliest four boxes. A lot of normal rarity weapons and rare rarity weapons that will never be useful to you and really basic early game treasure/materials. The weapons, in fact, can be automatically reserved for their EXP when you pull them to avoid forcing you to deal with tons of trash in your inventory (that's how worthless they are). It's complete filler... except, you also get the game's gacha currency from them, up until box #20. Pulling twenty boxes nets you 2000 crystals, which is 6 and 2/3 pulls.
Doing this is a bit of a slog, it's kind of a chore and one of the longer grinds a banner might give you. I kind of hate doing it, but I do it anyways because I want to get anime character jpegs for free. It is at least a little straightforward. The "raids" are only raids in the most literal, technical sense, except for the highest difficulty one, so what you do is set up teams that clear these "raids" in one click of the attack button without using skills. It's a browser game, so you can actually hit the refresh button to skip right to the clear screen and save a ton of time. The lowest difficulty raid gives you treasure which you use to host the moderate difficulty that gives far more tokens. You have to do this hundreds of times, though, so it takes several hours straight of grinding... it wouldn't be worth doing if you were busy or couldn't instantly clear the fights. Thankfully these story events give you crystals just for reading them, too.
Story re-releases don't do this, either. You grind treasure from fights, and then use it to directly buy items you want from a treasure shop. You don't get a lot of crystals from these, though.