Thank you, there are a few things I have overlooked. It would seem the ai favors lots of tiny ships where as I normaly start with medium size but never match their numbers. I am suprised that miniaturisation is so limited, I'm sure pre crusades u could heavily arm a medium ship that no longer seems possible. For example because I lack resources I have to use lasers and can only fit 3 if I want any defences and a warp engine. 

I don't even put engines on my warships most of the time. If you wanna build a defense force I recommend you do the same. There are plenty of techs that will give you +movement without adding engines on the ships.

To the OP, get yourself some resources, especially for your favorite weapon.  Claim them early and let them build up.  When you get the techs, use those weapons!  That is what changed things for me.  A further tip:  Be sure to get Durantium.  It lets you upgrade your mines and increase the yield rate of all types of Mining bases.  Makes a big difference, especially in th mid to later game.  This game insists that you think ahead.  Yikes!

To the conversation:

I have melded AI reaction into my strategy.  I basically ignore military and build as much infrastructure as I feel I can get away with.  If I can, I get the Pragmatic perk that gives me 50 turns extra of this.  Before that can get too risky, a subjective decision, I use my developing infrastructure to research military techs and get some halfway decent ships designed, and maybe even in the ship cues.

Then somebody attacks, or multiple somebodies.  After all, I have nearly zero military by their calculations.  It's an engraved invitation.  Whichever one arrives first may do some damage for a while, but they will soon face an initial fleet that can wander around and start taking their forward forces out.  Note, if they are all too close or other situations arise or Murphy's Law strikes, this can fail magnificently with a nasty gang up,  You have been warned!

If that works, then a second fleet gets formed.  If it is early game, my production may be low and that takes some time.  Generally, it will have later model ships.  It becomes the attack fleet.  It goes to the closest enemy and plays havoc with all defenders and starbases it can find.  

After that, I am ready to send Transports and Legions.  And I can claim that it is all their fault!

This does depend a lot on galaxies with space between empires.  If you play crowded maps, you are on your own.