With my first character I always died when there was more characters. No matter how much attack and defense I built up, a "fleet" with the same level always destroyed my ship with ease.
My solution was simple when I started my current character. I built up everything on a very strong shield. It is something around 7000 and regenerates at 100 shield per second, so it really protects me. After this I maxed out the Command and started to build up the other stats with items. It was a long way to gather the stat-increasing items but now my ship is strong enough for level 110 worlds and most of the enemies can't kill me if I fight.