One of the most basic things in League of Legends is learning the spawn timers of jungle monsters, minions and objectives. It helps increase your gold income when you don’t have to waste time waiting, and helps you prepare in advance to contest objectives like buffs or Dragon and Baron.
Lane minions spawn at 1:30, and a new wave every 30 seconds after that. Every third wave has a cannon minion, so if you intend to back to base or roam be sure to time it accordingly: your lane opponent will need an extra few seconds to kill the cannon minion therefore you have an extra few seconds to get back to lane before minions hit your tower. One other useful thing to know is that lane minions always spawn at the same time for both teams, so if you need to know how far enemy minions are from you just take a glance at the location of yours.
Wraiths, double golems and wolves spawn at 1:55 into the game and have a respawn time of 50 seconds.
Ancient Golem (blue buff) and Elder Lizard (red buff) spawn at 1:55 and have a respawn time of 5 minutes. Typically your (or enemy) jungler will start at blue, killing it at about 2:00-2:05, meaning the next time it spawns will be at 7:00-7:05. It’s an incredibly important time to note as it often allows you to pick up your own buff as fast as possible to prevent potential steals, or at the very least make sure your jungler doesn’t waste any time if he’s giving it to you. Additionally you can time jungle invades and catch the enemy jungler as well with a communicative team.
By being aware of respawn timers you can often determine the enemy jungler’s path and determine when he might gank your or some other lane. For example if the enemy jungler started at his red buff, at 7 minutes into the game chances are he’ll be there again, which may give you some breathing room to be aggressive in your lane.
Furthermore these timers are even more important to know if you’re the jungler, as it enables you to pick up your own buffs at the moment they spawn to prevent any steals, and when you’re feeling knowledgeable enough you can start to invade your opponent and attempt to take their buffs. Most junglers have a hard time ganking without their red buff so stealing it at 7:00 or 12:00 can significantly decrease their impact in the match.
Dragon initially spawns at 2:30 and has a respawn time of 6 minutes. Typically you’ll do it after your team scores a kill in bot or mid lane as fighting a dragon and your opponents in the same time is incredibly dangerous especially in early game. Even if the enemy team snags the dragon you should always try to catch the exact time when it was killed and type it out in chat. It’s a very easy calculation and reminding your team about the spawn time in advance makes sure they are prepared to contest it.
Baron Nashor spawns at 15:00 and respawns every 7 minutes. It’s the most valuable objective to take so having vision of it after 20:00 should be imperative. Even if your team doesn’t get Baron you should without exception note the respawn time and make sure to contest your enemies as soon as it spawns: farming bot lane in late game when Nashor is up is a sure fire way to give it to the enemy team.
A useful trick to remember if you didn’t catch the exact time of Baron’s demise is to take a note of when the buff expires on enemies: it last for 4 minutes, so Baron spawns exactly 3 minutes after you see the buff expire.
Knowing timers of monsters is definitely nowhere near advanced knowledge about the game and you should definitely burn the timers in your brain. It enables you to get small objectives throughout the game and extend your gold advantage over the enemy team, it helps you understand where enemies might be, and helps you and your team prepare to take or fight for important objectives.