Outfit for an investiture

[NewPhase23]

I'm going to an investiture (my own!) In mid March and need an outfit. I've sort of been in denial about it as this is massively out of my comfort zone, I usually dress very casually and haven't worn anything but trainers in years.

Money is tight so I'm looking for inspiration to guide my Vinted searching - brands, shapes etc. I'm a size 18-20 with a belly (this is why I've been in denial, like I'm going to wake up and be 4 stone lighter if I just ignore the impending date).

Shoes are a particular worry, I don't know I'll be able to last longer than 30 mins in a formal shoe, and I know there's going to be a lot of hanging around.

This should be something fantastic but is causing me masses of stress, both money and having my picture taken.

Any suggestions...?

Congratulations! @NewPhase23

I think @samlovesdilys 's idea of wide legged trousers, palazzo style, with a top and maybe a jacket or cardi type thing on top is a lovely idea.
Maybe a tunic top and trousers in one solid darkish colour and a nice colourful scarf and/or statement necklace.
This is an easy and elegant look and it works well with comfortable shoes.

I think this could look lovely in size 18.

Brilliant, thank you.