Ah Fortnite, Battle Royale. I've had several funny moments while playing with friends and having so called Llama dinners.
To the topic below though,
I would have to say nothing. Sure the skins and outfits look nice and all that but I'd save your money and if you got the save the world expansion, I would have waited. EPIC has stated that in some point of 2018, STW would be free to the public. Don't get me wrong, Battle Pass does grant you All of its many benefits and rewards but imo, spending money on Fortnite is alright if you get a discount or a sale for half off or something.
Also, here's the link to the official twitter of fortnite, incase you have any problems matchmaking or anything else or just is interested in any of the games news. (Not intended to promote in anyway)https://mobile.twitter.com/FortniteGame