Sorry to hear you're still having such problems, ckessel. I hope you're not getting too discouraged.
Like Revenantus, I strongly recommend force fields, especially in newer versions of the game. They're a fantastic investment and can be the difference between life and death in many situations. Previously, the AI was keen on sending in large amounts of ships and having them go after harvesters and the like instead of the really important targets, but it's currently a lot more interested in destroying the command station when it has the odds in its favor. A force field can help prevent this.
Furthermore, having a lot of cruisers and some fighters by your home command station early in the game when you're vulnerable is a really good call. The cruisers can take out incoming bombers, which are a serious threat because they're so strong against force fields. Fighters are helpful against other things, such as those raiders you were facing. If they're going after your harvesters with these good defenses around your home station, then exo-shields are another great investment. Force fields around your home station are basically a necessity, though, in my opinion. If the AI has ships immune to force fields, then you need to focus on ship- and turret-based defenses, probably with force fields supplementing this (but don't be relying on them in this case). It's also good to keep some fighters out by the wormholes, at minimum.
The expected pacing of the game is to take a planet about every 45 minutes; depending on one's skill level, the surrounding planets, and aggressiveness of the AI, you may over or undershoot this, which is perfectly okay. At the start of the game, there's a lot to do, with scouting, picking out what research to get, building a fleet of a good mix of ships, and setting up defense, so taking that first planet can take a while. Most important of all at this time is having good defenses set up (I typically rely on force fields and ships rather than turrets) since unlike later in the game, you don't have a buffer between your homeworld and hostile planets. If you're making an attack before 30 minutes, I caution that you should tread carefully, since you may not have the forces built up to support it (which is what it sounds like is happening).
Regarding things to research, you may want to throw some research at exo-shields, better force fields, Mk II fighters, and perhaps lightning turrets in the early game. I find Mk II fighters to be a good investment because they're cheap and durable and they're a great complement to cruisers, while the other three are great defensive items. One good strategy for wormhole defense is to put a force field right next to the wormhole with tractor beam turrets and other turrets beneath it. This can prolong the life of your defenses and keep the enemy from ever escaping the wormhole. Coupled with lightning turrets, this can be a really effective strategy. Also, I typically go for starships early because they're so powerful on both offense and defense; with one raid or leech starship and some attention paid to keeping it repaired, you can take over a Mk I world. Just watch your energy and resources, as leech starships are energy intensive and starships in general are pricey and could tank your economy if you're overzealous with them.
Finally, even though docks cost a lot of energy in recent versions, managing them has become a lot easier in some regards. Because granularity has been raised, it's reasonable to rely on one dock for a planet, boosted by some engineers, since now you're wasting very little time between ships (1/24 of a second rather than 1 second) and can efficiently build units without the costs of having lots of docks. You start the game with a dock and a pair of Mk II engineers, which is a great combination for pumping ships out quickly. Also, energy management is clearly important in the newer versions; a couple Mk II reactors at the start should be good for a bit, perhaps with a Mk I reactor, as well, but if that's not enough, then a Mk III reactor isn't the end of the world. Two Mk II's and a I are 30 resources per second for 69,000 energy, while a Mk III is 40/s for 80,000 energy, which may be more than you need that early. If you have a lot of power planets, you can just pause and unpause reactors as you need them in order to maximize your income at any given time; if you have to build that Mk III reactor, it's probably a good idea to pause the others on your planet.
Perhaps some of that will help with your strategy?