Damnit, I need help getting to orbit!
Guide to orbit:
2 Stage rocket, the first stage needs to be powerful enough to get you to around 40,000m. Conserve fuel, and once you've reached 40,000 meters detach and don't start moving just yet.
The second stage should be the classic 3 fuel tank and 1 engine. Position the rocket horizontally, and then throttle to the max until you've reached ~2300 m/s. Cut the engine, and you should still have a tank of fuel left. Keep an eye on the vertical speed meter, trying to keep the pointer at the 0 for as long as you have your engine still on to make the orbit more circular.
And voila, you're now in orbit. If you want to deorbit wait until you get the closest to the planet as your orbit goes and then rev up those engines towards the ground.
Okay, haven't played the game. Considered it until I saw it's a bit unoptimized. Not sure if I wanna put that much stress on my computer. I might stick it on an older one if they can meet the requirements though.
But, err. If this really has proper Orbital mechanics then...
Well, gravity doesn't seem to be implemented properly. You can tell if you detach some heavier rockets from you, and don't turn yours back on, or if you detach light things from you and keep your main rocket really heavy. Heavy things are being affected by gravity more than light things, which isn't how gravity actually works in real life (In real life it depends only on your distance and the mass of the objects exerting their gravity on you).
I think that's because they have more drag (items DO have a drag coefficient, I've checked).
Drag is definitely the problem here.
Heavy things are not at all affected more by gravity than light things, it's just that it takes more force to propel them than their light counterparts. For instance, when you detach your command capsule from the rest of your rocket, you'll be floating at pretty much the same level as the rocket for a while.