'Cocktail' dress code for wedding

[cfmtb]

You guys are amazing at this, so hoping for some magic!
I have been invited to a wedding where the dress code is 'cocktail'. Can't wear stilettos - only wedges/flats/chunky heel due to locations which may change dress options! Early September so weather should still be nice-hopefully!
I have loads of pre-baby dresses but nothing that now fits the bill!!
Early 30s, size 10, fairly big boobs so nothing that could have too much cleavage! Still self conscious about tummy area but could invest in some sucky-in knickers.
Budget isnt too big but might stretch if it's worth it!
Help
Also - for men, would you say standard suit or more tux for this?

I’m googling cocktail dresses but every link I click on just comes up with a load of very underwhelming dresses tbh. I always thought of cocktail as being that little bit more formal, but seemingly not!

www.easyweddings.co.uk/articles/decode-wedding-dress-code/

Cocktail is a suit rather than tux for guys.

I always look at ebay or the outnet for something a level up second hand rather than new. Any prefs in terms of colour/ brands/ styles?

@ItMustBeNiceToBeQueen I know! I'm having the same issue. I always assumed it was a bit fancier than standard wedding - floral midi etc

@Catandsquirrel suit it is, thank you! I like a longer length, midi or maxi. I used to go bright colours - red etc but not sure if that's appropriate for a wedding. I used to love Nadine Merabi, Lavish Alice style stuff but never have the place to wear any! Haven't bought myself anything nice for ages so I'm probably completely useless 🙈 I want something quite classy.

My gran used to have a 'cocktail watch' which looked like a bracelet. You had to lift a cover over the face to read the time.

And I remember feeling really silly once asking a workmate if she had got engaged when in fact she was wearing a 'cocktail ring'.

Stick a paper umbrella on your head? Sorry, these codes mystify me!