Hex Commander: Fantasy Heroes - Elves 1 - 10

Elven campaign 

Ballista - has the longest attack range of 8, good to chase defenders away from their positions.
Shadow Warriors - your main tanker. Little stronger and tougher than bears. But it moves faster through forest and roads. Additionally, has better range armor, while the distant attackers are a larger threat than melee.
Mages are little weaker than archers but has larger range which make them superior.
Healers - must have, but no more than 2.

Mission 1 - The Beginning
Considering you have only 2 gems, I suggest upgrading Arcaena. You will need her as a strong single unit in the next few missions.
Bypass Arandure as he will not move during 3'rd turn. 
Do not rush to the village, it would not be attacked until you enter it. First, kill wolves from the north.

Call a warrior and deal with wolves engaging from the east. Do not split your forces. Elvish defenders would all die, but women would run towards the north.

Mission 2 - Sapphire Stream
Bears are the problem. You do not have enough power to deal them in fair battle.
Use one gem to get a Healer and 2 to upgrades for Arcaena up to level 4th. Recruit a healer. Put Arcaena as a decoy on the forest, where only one boar can attack her at a time. Hide healer behind her and warriors, so they protect from wolves. Arcaena would kill all the boars while healed. The warriors that could not hide would die, though.

Mission 3 - Stream Ambush
Last Arcaena upgrade costs 2 gems, take it. It will help her survive. Buy 3 healers, one on each portal. 
Step your side sides warriors back, so only one enemy could attack them. If they survive first hit, buy them healers. They will draw some dwarves, so the hero would fight alone. Attack him with all warriors, while Arcaena decoys him forward. Get third healer for her. Run back from cannons and hide in forest. Check range of dwarfish units and canons, they would kill healers if you are not cautious.

Mission 4 - Rocky Path
The goblins are divided into 4 groups. You want to fight them separately.
Keep two archers on the hill near the road.
Move ale other units back and attack by the road.
This way, only one group of goblins would move against you. When they pass the line of portal, recruit 2 warriors to deal with mages. When safe, recruit a healer and cure all units.
Progress slowly with the road, and you will beat all other groups.

Mission 5 - Druid Circle Battle
You only need to kill Viviric. But bears will attack you even in the last turn.
It is hard even on normal. For this difficulty, rush against Vivirc and cast poison on the left bear to lower its damage. Then move around clockwise, so only one bear can attack you.
For highest difficulty, either protection scroll or regeneration potion. Scroll protects from damage and from weakens. Regeneration allows for can hit-and-run as Viviric does not move.

Mission 6 - Defence of Calyril
Hide behind a wall. Recruit 4 healers. Do not forget about 2 chess. One in the centre, one near the western wall.

Skirmish mode.

Having four units unlocks skirmish mode.
Pass normal and hard with just Arcaena and single healer. It gives you gold and any scrolls and potions you find in chests.
You may leave one enemy and safely collect all treasure on the map.

On extreme, you get free gem. But healer only is very tricky. Get 3 ballistas. Set them in line while Arcaena keeps enemies busy.
You may buy ballistas in far away portal or throw some elven warriors to stop orcs further.

Mission 7 - Four Fang Hideout

At start, You are attacked from 3 directions. Main army from east and wolves from north and south.
Recruit 1 ballista and 5 warriors. Fall back with ballistas and healers, and surround them with warriors. The start is though, but if you have problems upgrade both ballistas and mages, and it shall do.
After you survive the initial attack, the rest should be east. Just do not split your army and keep full health with healers.

Mission 8 - Runaways

Rush Arcaena to outpost. She will get control of those units. Setup all 3 scorpions on the northwest cliff. One scorpion is already there.
Buy one healer and send it scorpions.
Put all other units above the portal. Sylvius bind skill will stop any orc that passed the scorpions.

Mission 9 - Blocked Road

Upgrade both bears and mages. Recruit one Batista and two healers. Defeat enemies by groups.
First the north one, which is already attacking you. 
With 3 mages on the west hill target archers. But fall back, so you get first hit vs orcish shamans. Hide main army in the trees. Orcs can not enter forests unless they stay next to it, so you will get first strikes.
Secondly, focus on the 3/4 archers hanging on the east. Arcaena would deal with them alone.
As third, kill the tower archer orc, but do it in one turn. 2 mages is enough. If you do not, the whole camp would get speed potion and attack you.
You can reach elves on the other side by sneaking. If you do, they will join. But orcs will attack them immediately. Best set up your forces against the camp and use ballista as soon as you meet with eastern force.

Mission 10 - Artisan Argument

Normal is against elves, it is easy. Be sure your ballistas kill theirs, not otherwise.
Hard vs human. Your range is better, but cavalry is a problem. Arcaena will deal with them, Sylvius would need some work. Do not let your heroes be frozen by enemy mages.

Extreme is vs dwarves.

Recruit 2 ballistas on both paths. At north get a healer and on south a mage. Sylvius will do healing on the south. His range is longer than healer and mage has longer attack than Sylvius.

There are two mortars hidden in the center hill. Both can be shot from northern path. Seek a field north of the road, just as ballista gets in range to mortars. 
Get your ballistas in range of artisans and you win.