ROAMING & TEAM FIGHT
Summoner spells are a big deal since ignite can win you the 1v1 due but teleport can sometimes win you the game. It depends on your match up, but following this guide as Aatrox, if you are fighting a strong enemy duelist like riven then you will need to take ignite to be able to win those trades. If you fight a tanky enemy like Dr. Mundo or Volibear then teleport would probably be the better option. Using teleport at bot lane and doing it correctly can get your team ahead by taking dragons and towers. Once you get out of the laning phase the team fighting and skirmishing phase will begin in the game.