but idk what offset wheel is
Wheel offset is a measure of how far from the center of the wheel the hub connects to the wheel, thus allowing the wheel to either sit farther in or out. An offset of 0 means that the hub connects to the wheel at the center (the spokes of the wheel are recessed to the middle of the wheel), a high offset brings the spokes towards the outside (stock wheels have a high offset) a low offset brings the spokes closer to the center (allowing the wheel lip and tire to sit farther out making it appear flush)
OP: Lowering your car is not as simple as putting the springs on.
The best springs to get would probably be coilover sleeves since the height is adjustable, but I have heard good things about the Tein S-tec.
The stock struts are made for stock ride height and they are not the best for lowering, however coilover sleeves will not work on them. Most aftermarket struts are good (I recommend Koni, but Eibach, Blisten, and Tockio are all great) but you have to pay for them, and the lowering springs wont work on them...don't buy any poor quality cheap stuff or you'll regret it when the ride is absolute garbage and they break a month later.
A set of coilovers would be best since they include both the adjustable springs and a strut, and they are already put together.
After you get lowered, you need to have an alignment to keep your tires from abnormal wear. Also a camber kit is recommended but not required, which adjusts the angle that your tires make contact with the ground