Well if you want costs down and something that pulls together without a dodgy theme-
look in the garden (or someone elses if your is as bland as mine) at the colours there. That's the ones you want! Will keep flowers cheap (seasonal = affordable), and give a really pretty feel.
For example, doing that now I;'d have bouquets of pink roses and levender- wow! how wonderful? And that's a colour scheme that could be worked for most people (if you wanta colour scheme- you can of ourse just pick a dress and get it made in peoples personal co-ordinating preferences).
love the cake, when I was with XP we were palnning a summer wedding and chose a willow pattern coloured cake with iridescent white butterflies, however I ahd the fortune to amrry the son af a wedding cake designer who had just won national award LOL- mine was white with wonderful lemony bouquets amde of sugar that amtched my flowers (and were so relaistic everyone thought were real)- with beautiful bumblebees for fun (she added those, theyw ere fab). We amrried in Amrch though so ahd spring colours.