Always, always use layers or you will end up crying if you don't. Honest, trust me here!!

I can confirm this. I created an entire draft cover with some very specific dimensions, then went to start adding effects to specific parts. It was all on one layer, so I couldn't get any of it to behave right.

I ended up scrapping the cover and going with a more minimalist design anyways, since my brother pointed out my original "looked like it was made in ms paint". But, lesson learned. Layers!