Prize giving outfit help

[Whatdoesaduckdo]

Long time lurker first time poster
Outfit help desperately required
My eldest is receiving several prizes at her Grammar school prize day this Thursday. The invite states "...to mark this prestigious occasion by dressing appropriately .... No denims should be worn"
I live in jeans Breton tops and converse what do I wear?
I am a curvy size 12
I live in N Ireland so not all shops available to me and delivery can be slower on internet shopping
All advice greatly received

Let's start from the bottom up. What smart shoes do you own?

Shoes wise I have
Black patent high heel Jasper Conran Mary Janes
Ballet flats in most colours
Mink coloured suede closed toe wedges
Tan coloured suede closed toe wedges
2 pairs of black court shoes - one mid heel and one sky scraper

Are you comfortable in a skirt / dress?

Skirts are fine
I love the idea of a dress but only ever wear for weddings as I'm never sure of getting it right in terms of style ie too formal / casual

OK, so sounds good on the shoes front. So if you don't fancy a dress, then you could either do a nice top with a skirt (pencil skirts look stylish) or a nice top, jacket and skinny trousers. What colours do you suit (black only suits about 10% of people when worn near the face!) and what's your budget?

Just to throw something out there, this skirt would look good with a navy top and black patent heels.

www.next.co.uk/x5438s2#692914x54

I generally stick to navy, green and cream colours
Budget would be up to £100, £150 at a push

The skirt looks nice - good length and there is a Next in our local big town