While everyone says RO has a steep learning curve, what never gets said is that the curve plateaus fairly quickly.
This is important because it means that after a few weeks, you will be doing very well. There are no ritalin-twitch 10-year olds pulling off crap that you will NEVER be able to do. That garbage fails miserably in RO, which is what makes it such a great game.
In my experience, there are two things that really improve your game. One of them is controllable, the other often isn't.
1) Learn the maps!
You can always tell a new player, even from far away. That's because they have a tendancy to stand around in the worst places. They simply don't know which spots are dangerous. When you learn the maps, you will eventually be able to shoot pixels because you'll know where to expect the enemy to be.
2) Better equipment.
Sorry, but it's true. A better monitor, better mouse, and lower FPS will improve your game. I went from being usually in the middle of the scoring pack to almost always at the top right after I bought a fancy new computer with nice peripherals.
The most enjoyable way to play this game is to be the best you can be after considering 1) your experience level, and 2) the hardware you have.
By the way, you will ALWAYS get hit from somewhere that is a complete mystery to you. It happens. But soon you will do the same to the enemy. You'll see....trust me.