(Couldn't find a better background) Potential "Log-In" in the bottom right corner, The title of the game somewhere on the top left
Most likely some sort of skip-able cut-scene just for the players to get a basic understanding of whatever is happening, as well as a basic understanding of how to play. (Please imagine the screen as a camera turning on as I couldn't find something similar to that)
Probably a character select screen with four different tabs of characters, "Tanks", "Damagers", "Supports", and "Wildcards". Most likely a tutorial select at the bottom right if the player requires it. (Please imagine more characters, thank you.)
Selecting a character would then put you into a lobby for you to invite your friends if you want to play with teammates and decide on whatever mode you want to play (at the bottom right, also).
Ready to Go!
Once all players in your lobby are ready, you'll start searching for a match of 48 players in a large arena (including you [and your friends]).
(Had to make the background because I didn't find a suitable one) The Victory Condition is to be the last standing, even you're playing with teammates, you have to fight them, too.