Up until chapter 6 (dwarves) I had 6:3:1, but I had steel boost which makes twice as much as your marble(and is twice as big)
After that the basic rule for me was that every time I upgraded my Tier 1 buildings to a new size, I deleted one.
Until chapter 8 where I was at 3:3:2, but added a T3 for 3:3:3 and stuck with that for 4 chapters
It wasn't until chapter 12 that I dropped to 2:2:2
For your military, it's your barracks that increases
speed of training. The only purpose of armories is to keep your barracks running 24/7 while you are AFK. This means that everyone needs a different number of them based on schedule.
The basic method for this is to max out your barracks, then fill it and see if the total cooking time is longer than you plan to sleep.
You can also use this calculator to figure out what combination of max barracks and armories you need to maintain the queue time that you want.
www.tinyurl.com/trainingcalc
EDIT: I had a look at your Aren city, here:
http://www.elvenarchitect.com/city/planner/095e7e3df09847789d824ba744f52405/
and there's really nothing I would change.
Your 8 marbles are fine, and when you unlock level 15 marbles you can have 6 of those instead, making 100% more than you are now.
(plus any increase in your boost % from relics)
I think your training queue is just over 6 hours, so probably a focus on maxing out the barracks and levelling your armories should do it for now.