It'd help to know what you already have.
The .223 is going to get blown hither and yon in the wind. In some ways, that's a good thing if you're trying to learn to shoot in the wind. The problem with .223 is that at longer ranges it's very difficult to spot either hits or misses. That little bullet just doesn't make much impact, so you don't get much indication on steel or in the dirt unless it's really dry and dusty.
Unless you already have one, I'd have something in the .243 or .264 families. They have bullets available with good high BC's and are relatively cheap to shoot.