After completing the tutorial, you will be able to pick their first Warcraft Rumble leader! You'll be able to pick from three different randomly selected leaders. An opportunity to choose another isn't too far away though, so don't worry if you don't get the leader you were hoping for.
First Leader Choice
Early in the game, you'll want to pick up a leader that is able to take some damage.
Baron Rivendare is a strong choice early on, as he frequently spawns skeletons from structures that you control. The skeletons are useful for slowing down incoming enemies, capturing chests, and controlling the map.
Tirion Fordring is another strong choice, as he is a tank that can also heal nearby units. As long as you keep him surrounded by other units, he'll keep a push going.
Grommash Hellscream is a great choice, as his Bloodlust passive grants 33% movement and attack speed to all nearby units. He is strong in a group and should be used with a wave of units.
Hogger is another good choice, as he is easy to play. Just keep playing him as often as possible, as his movement and attack speed increase 35% each time he is played. He cleaves nearby enemies and is best used in a group of units.
Cairne Bloodhoof is a very high health leader, giving a 20% health buff to your other Horde troops. He can stun and do AoE damage.
Rend Blackhand is a strong leader if you have other flying units. He'll reduce the cost of other Flying troops by 1 Gold while in play (but no less than 2). If you don't have other flying units, he may not be the best choice.