If you are a player that uses 1 city for both attacking and defending then here are some basic rules of thumb that will help you with getting results.
First off, defending:
You should start by having your best purple gems on your RING and then SHIELD (in that order). Your WEAPON, CLOAK and AMULET should all have your highest GREEN and BLUE gems. Your goal is to get your LIFE and -FOE ATTACK DEBUFF as high as possible and as equal as possible. Gear choice is always up for debate but use the same rules of maxing out your LIFE and FOE ATTACK DEBUFF.
Many people feel differently about the troop types but for the best/safest results I would keep the troops limited to to T1, T3, SOME T5, PIKEMEN if you so choose and then lots of MASTER RANGERS and MAMMOTHS. Always make sure you have ample amount of gold in city and that you never open if you aren’t going to be around to monitor.
You should start by adding your best purple gems to WEAPON and AMULET (in that order). Your CLOAK, SHIELD and RING should all have your highest RED and ORANGE gems. Gear choice is always up for debate but use the same rules of maxing out your ATTACK and -FOE LIFE DEBUFF.Your goal is to get your ATTACK and -FOE LIFE DEBUFF as high as possible and as equal as possible.
Troop choice is dependent on who you are attacking so pay attention and always remember
FOOT > MOUNTED > RANGED > FOOT
Monitor your incoming and outgoings. If you aren’t getting a positive ratio of might kill vs. might lost then either stop attacking or close your city.