Styling Help with Alloy wheels

[fv43576]

I have bought other same Punto HGT diesel, this time I want to change my own alloy wheels 15 inch not 16 or 17inch because of low profile too harsh ride for me, the tyre size is 185/55 but what is the best alloy anyone can recommend to me?
I saw a OZ ultraleggera said 10% lighter than any others alloy. So if I get light alloy will it increase better accelerate or better MPG or improve handling?