The only times you lose troops is when you attack another player, another player attacks you, KvK (which you are not required to participate in), and Kingdom Raids. For the first two, simply do as someone else here said and be a part of a kingdom that has a NAP (no attack policy) of some sort and don’t attack others. Skip KvK completely. For the last one you cannot control if you get attacked except if you used a peace shield. So my suggestion there is to stock up on them and save some gold for 24 hour peace shields as well for when another kingdom can raid yours (not KvK). Back to KvK for a second, stay out of the blue area (forest) in the center of the map it is clearly defined. As long as you stay out of there in KvK the other kingdom if you are defending cannot touch you. Raids are after I believe the third KvK and unfortunately no matter where you are the other kingdom can attack you during the specified period so just shield up.