TL;DR: Keep gold low, spam miners, swords, archers. If CA, Spear.
The BRIEF but COMPREHENSIVE GUIDE:
Alright, so since there's tons of new players (newbies) and maybe some of those who are just frustrated at being stuck on 1200, here's what you do that exemplifies concepts - forget about strategies and so forth.
1. Make Archer/Miner on every map to start.
2. Make miners, swords and archers.
3. Keep your gold low (otherwise it's just being useless in the bank!)
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This should get you through most of the earlier ranks. As long as you make consistent miners, swords and archers (which keeps your gold low), you'll be fine. If required, put 1 on mana and make a spearton of he goes CA. Below is what you do when the players get a little better and you can't end it so fast.
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4. @9 Miners, put 1 on mana.
5. Keep making miners and archers.
6. Save for a spear when you get 50 mana, then buy one.
7. Keep making miners until you have 14.
8. Make spears, archers and hustle.
9. Win.
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SO basically, focus on making as many "stuff" as you can. At lower ranks, as long as you have more "stuff" you can win due to sheer size of army. TL;DR Method at the top.
When you feel confident you can make units efficiently, watch this video on G-kiting, essentially the most fundamental micro move in the game.
https://www.youtube.com/watch?v=ZeJnL6fBj-g
Grats, you're now set for 1800 ~ DAZ