For me, xp that you win in a battle also should go to the race that you are using. You con do that the free races (Elves, Snow Giants and Legionaries) can lvl up till lvl 3 for example.
The lvl should give races some abilitis like this:
Elves:
lvl 1 --> nothing
lvl 2 --> +0.5% extra defence
lvl 3 --> +1% extra defence
Legionaries:
lvl 1 --> nothing
lvl 2 --> +0.5% extra atack
lvl 3 --> +1% extra atack
Snow Giants:
lvl 1 --> nothing
lvl 2 --> +1% extra atack -0.5% defence
lvl 3 --> +2% extra atack -1% defence
The other races (the ones you have to pay) should have more levels and diferent bonuses. This will make that payed races with no bonus will start to be usefull (in my opinion, this will increment the amount of coins that people buy).
So, for example, the races colud have this bonuses:
Soldiers:
lvl 1 --> nothing
lvl 2 --> +0.75% extra attack
lvl 3 --> +1.5% extra attack
lvl 4 --> +2.5% extra attack
lvl 5 --> +3.5% extra attack
Robots:
lvl 1 --> nothing
lvl 2 --> nothing
lvl 3 --> +1 total attack boost (so you can use in a batlle 4 attack boosts)
lvl 4 --> nothing
lvl 5 --> +1 total defence boost (so you can use in a batlle 4 defence boosts)
Elementals:
lvl 1 --> nothing
lvl 2 --> +0.75% extra defence
lvl 3 --> +1.5% extra defence
lvl 4 --> +2.5% extra defence
lvl 5 --> +3.5% extra defence
Pirates:
Well, pirates you can do that the can attack terriotors out of reach by using their ships. this is to strange for the game, so for me is better something more normal like this:
lvl 1 --> nothing
lvl 2 --> +1 starting unit but you are allways the last one who places units
lvl 3 --> nothing
lvl 4 --> nothing
lvl 5 --> +1 starting unit (the penalization of lvl2 is removed)
Ninjas:
lvl 1 -->nothing
lvl 2->+1%of chances of evading an atack(you dont loose units and the enemy looses 1, he can atack you again if he wants
lvl 3 --> +2% of chances of evading an attack
lvl 4 --> +3% of chances of evading an attack
lvl 5 --> +4% of chances of evading an attack
For the ninjas i was also thinking of something like this:
lvl 1 -->nothing
lvl 2 --> +1% of chances of counter attacking (if you are attaking me, now mi region attaks yours)
lvl 3 --> +1.5% of chances of counter attacking
lvl 4 --> +2% of chances of counter attacking
lvl 5 --> +3% of chances of counter attacking
Angels:
lvl 1->+1%defence bonus +5% chance of having another 1%defence bonus(so if you are luky, you will have 2%defence bonus
lvl 2 ->+2%defence bonus +5% chance of having another 2%defence bonus(so if you are luky, you will have 4%defence bonus
lvl 3->+3%defence bonus +7% chance of having another 3%defence bonus(so if you are luky, you will have 6%defence bonus
lvl 4->+4%defence bonus +7% chance of having another 4%defence bonus(so if you are luky, you will have 8%defence bonus
lvl 5->+5%defence bonus +10% chance of having another 5%defence bonus(so if you are luky, you will have 10% defence bonus)
Demons:
lvl 1 --> +1% attack bonus +5% chance of having another 1% attack bonus (so if you are luky, you will have 2% attack bonus)
lvl 2 --> +2% attack bonus +5% chance of having another 2% attack bonus (so if you are luky, you will have 4% attack bonus)
lvl 3 --> +3% attack bonus +7% chance of having another 3% attack bonus (so if you are luky, you will have 6% attack bonus)
lvl 4 --> +4% attack bonus +7% chance of having another 4% attack bonus (so if you are luky, you will have 8% attack bonus)
lvl 5 --> +5% attack bonus +10% chance of having another 5% attack bonus (so if you are luky, you will have 10% attack bonus)
Insectoids:
lvl 1 --> +2% chance of spawning 1 extra unit in a random region (after second turn only)
lvl 2 --> +5% spawn bonus +4% chance of spawning 1 extra unit in a random region (after second turn only)
lvl 3 --> +5% spawn bonus +6% chance of spawning 1 extra unit in a random region (after second turn only)
lvl 4 --> +10% spawn bonus +8% chance of spawning 2 extra unit in a random region (after second turn only)
lvl 5 --> +10% spawn bonus +10% chance of spawning 2 extra unit in a random region (after second turn only)
In lvl 4 and 5, you can spwan 1 or 2 units. so in lvl 4 for example, you have 8% of chance of spawning 1 and then another 8% of spawning another unit.
Obiously this bonus dont stack. For example Elves have 1% extra defence in lvl3, not 1% + 0.5%.
The numbers i put and the bonuses that i have invented should be balanced after testing them a bit, and they dont necessary need to be like i imagined. Finally, its all up to the programmer to decide if something like this can be done or not, and what changes are needed to be done.
Well, thank you for reading.