Someone really does have to make a beginners guide. Maybe I'll do that some time this week. Unfortunately, it's not going to be "short", because there are a lot of subtleties in the game.
On the military front, near the start of the game you should try to access higher level military units. You shouldn't build large forces of light frigates (or really any unit for that matter) because it will leave you vulnerable to being countered. Your fleet should consist of at least two unit types built in bulk, preferably three. The favourite combo is usually long range frigates and flak frigates, but you can get away with light frigates and scouts. Remember that scouts are very weak and cheap so you need to build them in great numbers to get effective combat performance out of them.
On the economic front: colonize colonize colonize. With the exception of some of the low-lying fruit, economic technologies are a really poor investment. Logistical structures (with the exception of extractors, those are literally gold mines) are similarly too expensive in the early game. Expand voraciously and capture new planets to increase your income. Introduce trade later on when your empire is already large and somewhat mature, because it will take around 20 minutes for your trade port to actually pay off its initial investment.
On the defensive front, you should try to lean as much as possible on your fleet. The best defense is a good offense; it keeps your enemy fleet wary of a counter-attack and you can move reposition your fleet regardless of where the enemy strikes. You should use repair bays as part of any static defense lineup, and build them in bulk. They are cheap, they are efficient, and they are versatile. Whenever I go on the offensive, first thing I try to do is take out the repair bays. If they're not out of commission before the enemy fleet shows up, I probably have to make a hasty retreat.
