it comes down to the gold fury and fire giant above all else really. The Gold fury is easier too kill than the fire gaint and it gives your whole team experience and gold, which leads to your team getting stronger than he enemy team. The ADC (a character that does a lot of damage with his basic attacks) and support ( a tanky character that should have a lot of CC that's used to set up for their allies) lane next to the gold fury so that if they get ahead they can try to take it. This can happen as early as the 5 minute mark if 4 people work together. The support needs to be on that side of the map because they have Wrath of the Gods aka HoG 3. That can kill the gold fury and fire giant instantly when they reach 25% health ( when their health bar turns yellow). So early on you you want your support close to the gold fury in case there is an opportunity for your team to take it, or he can prevent the enemy team from taking it. Sometimes if the the support just shows his face while they are trying to do the gold fury, they will stop and run away as they don't want to risk him stealing it with his HoG. SO that's why Support is there, but adc's are also weak in the early game until they get enough items where they do a lot of dmg. Support have higher base dmg so they don't need items to do good dmg early on in the game, just higher levels. So supports help the the adc for the first 3 minutes so that the adc can be in a good spot, then supports just roam to mid and duo lane. Mids are mages because early on mid lanes have the most team fights. Usually 3v3's with supports, jungles, and mid laners fighting each other. Mages provides good AOE dmg from a save distance. They use their AOE's to fight over the mid harpie camps which is a confined space. Junglers jungle because that's their main source of xp, from the camps, and if you don't have a jungler the enemy will and he will just control the map and get a lot of free farm from your camps. That leaves solo laners. That is actually the most diverse lane as we can see Warriors, Mages, Assassins, and even a handful of guardians. It really comes down to rounding off your team with the solo lane character, or a character that can pull off a particular strategy. But because Fire Giant doesn't even become an option till about 15 minutes in, and that is risky even than, there is only one person left to that side of the map because you don't need to really defend that side of the map until about late-mid game.