[Alneyan]

I would expect your problem to be expansion; an aggressive expansion is mandatory in the game, though the AI does not usually shine at it.

The rough guideline on expansion is to go as fast as possible, and then a bit quicker than that. Having twice as many planets as the current turn number would be a good start (so 100 planets on turn 50), though certainly not the easiest thing in the world to achieve.

You should use your first colony ships to expand forward, two or three systems away from your home, if not farther away. Ideally, you will have one or two spaceyards on these places a bit after turn 10, and will be able to produce other colony ships to further expand your area of control. You should only develop your economy as needs arise in this stage of expansion; a few facilities should be all that you will need to fuel this first wave.

The main purpose of an outward expansion is to control as many systems as possible, and/or to establish an easily defended border. For example, if there are only two systems through which an Empire can attack you, defence should be much easier than if you had ten systems to defend at once. Once you have established this perimeter, developping your colonies will be much easier. Mines make the perfect defence against early raids; these require you to research Construction, and then Mines (at least up to level I).

The above was very generic advice, as a typical gamefile would help to see the problems of your Empire, and I am reluctant to tell you too much at once (both to leave you discover part of the game, and because a lecture on economics would not exactly be easy to assimilate in a few minutes).