A dress for the races

[maitaimojito]

I've just been invited to the races by a work client and online searches for a suitable dress have left me confused.

I'm a size 10-12, twenty-something. Average height, average chest size. I don't tend to go for anything too bold and outlandish. It's at the beginning of May and I have to get the train so I'm also wondering about my options for jackets/coats and shoes.

I can't seem to work out what sort of styles women my age would wear to the races. There's a fine line between looking like you're going for a night on the town and looking like you've borrowed your mum's dress

Does anyone have any ideas on where I could look. Budget