Stay very small. Load the front and sides with weapons, then load the back with boosters. Some of the large ships are designed so that you can usually just sit in front of them. Their guns will be far enough apart that they will not be able to touch you.

Ignore the green parts you start with (except one engine). Place that one engine on the back of your pod. The pod laser is two levels better than green. Ignore the green ships and go after a yellow or orange one; they will ignore you until you attack. Ultimately, you must have red or purple guns or engines. If you make a mistake, strip down to the pod with a single powerful engine and a purple gun.