The idea is to facilitate the learning curve by facilitating the retention and calculation of units and technologies, let’s start with what they have done well so far
what they have done well
1) The costs of units and technologies are multiples of 10 and 5, which facilitates the calculation since multiplying by 10 and 5 is relatively easy
2) Most units and technologies require two resources, if any require three resources make two of the resources cost the same, that makes memorization easier
3) 3) The total costs are similar or are multiples, for example the total cost of the manual artilleryman is the same total cost of the royal knight (240), the total cost of the crossbowman is the same total cost of the horseman (120), a particular case with a unique unit the total cost of the Fire lancer is equal to the total cost of two archers or two spearmen (160, that makes it easier to memorize the cost of unique units)
4) Several technologies of the same age have the same costs, for example I found, several technologies of the age of castles, unique or not all of them cost 100 wood 250 gold
What needs to be improved
a) Equalize unit costs as in the case of the longbowman, it costs more food than the normal archer because it has more range, but if you make it cost the same as an archer, 30 food 50 wood could balance it with life and time of production
as mentioned the cost of a unique unit must be equipped to another, if it cannot, make the unique unit cost the total cost of two units, for example the cost of the streltsy, if you make it cost 100 food 100 gold, that would be equivalent at the total cost of a spearman and an archer 120+80 =200, to compensate change other variables such as damage, attack speed or life, if it is a prime number or it does not matter, they are not learned
It is not relevant that the life of units is a multiple of 10 or 5, as in the long archer example, if it cost the same as a normal archer it would not matter if its life decreases from 70 to 69 or 68, nobody learns the hp of units, rather variables such as hp, production time, attack speed can technically modify them because nobody learns them, change that so that the cost of the unit is easy to remember trying to find units of the same category cost the same
**b)**the technologies that require three resources, you modify two of their resources so that they cost the same, that facilitates memorization as already mentioned
c) make both resources end in 0 or end in 5, that facilitates memorization, imagine that one technology costs 150 food 225 wood and that another technology costs 155 food 220 wood, that makes memorization difficult, I give an example of two technologies, one French technology that resources end in 5 and a Russian technology that food does not end in 5 so I add 5 to food and compensate with three seconds less
Conclusion
If the rate will be two civilizations each year, I hope you take my observations into consideration, to facilitate the learning of various civilizations
In short, make both costs end in 0 or 5, that units of the same category cost the same or the multiple of a unit or the sum of two units, that as much as possible the technologies of the same era cost the same resources , if a unit requires three resources make two resources cost the same
for example i do know horseman and man at arms costs more food so i go collect lots of food if im gonna make archers i know i need wood i go collect it so i dont think too much about the what they cost but its nice thinking to make thinks easier 
