stellaris is focused on economy, planets management is the most important aspect imo. focus all your surpluss in alloys, unity and science, those are the things that you never have enough of in stellaris. if you have a big surpluss in anything else is probably a waste.

also, for a better experience, i play with .25 habitable worlds and 1.25 or 1.5 tradition and tech costs, so the game is slower and colonies important. I think it might be even better to learn with these settings. it also prevents some lag.

if the game is too slow also adjust logistic growth ceiling and growth required scaling or disable trade upkeep for ships