What's the consensus on how to upgrade your gunpowder units for effective fighting? Lately I've just been going with straight combat strength so I can be offensive or defensive with the unit and only going for city garrison promotions for a place that is likely to get hit with a stack of doom.
Has anyone found some combinations of promotions for them that work well? City Raider promotions work so well in the early game. I also notice when you upgrade an old CR unit to gunpowder it still keeps that promo, and becomes very deadly.
I definately like pinch later on when the foe starts having gunpowder units everywhere, but what about before that?
City Raider is a great promotion to have, but you can get this only if the gunpowder units originated by upgrading from medieval units.
As you mentioned, the Combat line of promotions is a good all-purpose approach to take. However, it may be helpful to mix this in with other promotions.
For instance, if a gunpowder unit has 3 promotions to begin with, I find it useful to spend the first 2 promotions on Combat I and Combat II, and the third promotion on one of the following:
1) Combat III
2) Formation
3) Pinch
4) Medic I
5) City Garrison I
There are exceptions to this guideline. Since the Medic and City Garrison lines can go beyond level 1, I will have some units specialize in these, instead of the Combat line. I generally have 1 unit per city specialize in City Garrison, and 1 unit overall specialize in Medic (it needs to be a leader unit in order to get Medic III).
What I rarely do is dabble in different promotion lines for a single unit, unless one of those is Combat. For instance, I will rarely ever give Pinch AND Formation to a single unit.
Apart from the exceptions, my gunpowder units will take Combat as the main promotion line, with 1 slot possibly spent on something else. So, continuing with the 3-promotion example above, I will have one of the following:
Combat III, 1/4 of the time
Combat II + Pinch, 1/4 of the time
Combat II + Formation, 1/4 of the time
Combat II + City Garrison, 1/8 of the time
Combat II + Medic, 1/8 of the time
This applies to the age of Cavalry. For units from the age of Tanks, it becomes:
Combat III, 1/2 of the time
Combat II + Pinch, 1/4 of the time
Combat II + Medic, 1/8 of the time
Combat II + Drill, 1/8 of the time
With a Protective or Aggressive leader, I use a similar strategy, except that all units will be 1 better in Combat, City Garrison, and/or Drill. I will also have a few units specialize in the Drill promotion (but only in rare cases).
I have found that having the Red Cross national wonder can provide a lot of free promotions to units that otherwise need to spend a promotion to get Medic I. Once I get Red Cross, I generally have the Red Cross city's units specialize in Medic, and units from other cities don't even bother with Medic.