[2.5IL Guide] On How to Finish the Map

Team Composition

Team of 4 Players

1 Tank 1 Support 1 DPS 1 Caster / Summoner

Team of 6 Players

2 Tanks 2 Supports 0/1 DPS  1/2 Caster 0/1 Summoner

Team of 8 Players

2 Tanks 2/3 Support 2 DPS 1/2 Casters 0/1 Summoner

As third support you need one that can give mana regen to the whole team so you can even count a caster like Jaina as support even tho she has only one support skill.

Team of 10 Players

2/3 Tanks 3 Supports 2 DPS 2 Casters 0/1 Summoner

Team of 12 Players

3 Tanks 3/4 Supports 2 DPS 3 Casters 0/1 Summoners

Notice heroes such as Medivh can be played as Sheep Killer / Boss Locker and overtime AOE damage if you build him as a caster.
Many more heroes can be played out of their specific roles or just be played as greedy as Agrypnie can

I do not recommend picking Summoners or heroes like Sylvanas with more than 8 players as the game will be unplayable due to all the summoned units.

Team Leading

You will always want to have someone to lead the team.
For example I always propose 100 at start so people can buy Bloody Key and ask them 120 in return.
Why 120 ? Cause if I only ask 100 I won't be able to get Bloody Key myself.
Also you have to know how to prioritize if you lead :
-Do you have enough time to do this extra objective ( raid boss, roaming boss or sheeps ) ?
-Is your team killing the buildings / units / right bosses fast enough ?
-Did everyone got the information to go to the objective you called ? Don't blame people, they're just tunneling, which is normal ( Ricotico we love you <3 )
-Is everyone in the good spot to be efficient enough ?

Team Itemization

During your game, some heroes will need to pick specific items they need for themself.
I'm going to talk about what items you need in a global way. I'm not going to talk about specific builds as I'm more of a team oriented person ( Main BlitzCrank Top Mid Jungle and sometimes also Support ).

Early Game Items

Bloody Key is the first item you want to get
Boots of Experience are also a must have
Taking an orb as melee hero is also an impacting choice on your game
Only 1 or 2 persons should go gold mine ( more recommended wich Acolyte or Peasant in the game )

Beginner Pendant of Mana is a must have if you don't have much mana regen in your team and even more needed if you're playing tank
Golden Key should only be bought by heroes making huge amount of kills ( which you can track on the "Player Informations" board )

Now you can either chose to make Dual Key or Sunny Key or both. Depends on what you need/want.
Oh and Bloody Key being different than Dual Key, they both work together

Mid Game Items

Silver Slaughter for those who have good amout of kills like dps heroes
Experience Boots (Upgraded) = more powerfull spells and global stats
Other Stats scalling boots if you want more stats ^^
Firely Egg of Corruption ( Must Have )
Staff of Resurection (Must Have)

Late Game Items

Jaina's Staff if mana regen is still needed
Healing Ward if not any for of regen aura is present in the game
Flag of Courage (Must Have)
Banner of Victory (Must Have)
Amulet of Kadghar as Caster is a really good item to avoid dying ( Tank shop )