The difference between the 215/50 and the 225/50 is the tread covers wider areas on the ground, giving you better handling and grip. Hence the 225, which is the width of the tire. The 50, signifies how thick the tire wall is. Higher the number, the thicker the wall is, which adds more ride comfort on the road. Lower the number, the rougher the ride is. It's not necessary but if your car was lowered, it factors in how much clearance you got from the fenders and how much space you have from your shocks/struts. Coilovers only lowers your car further down, and adds stiffness, minimizing body roll and understeer depending on the car. That's why I was asking if you had coils because you will need to roll your fenders and get spacers if your car is lowered on coils.
Coilovers or shocks/struts, are the primary suspension of your car. If you don't know what they are, here's an idea.

These are the shocks and springs.
If you're not going to lower it, you don't need to roll the fenders. At most, you might need to get some 5mm spacers just to be safe to clear the clearance between your tires and your shocks. Why don't you try having it test fitted at your local wheel shop that sells these rims. I'm pretty sure they will give you some good advice on what you need to do to make them fit.