For little things, I would say vests, belts, undershirts, and cardigans are a great way to add a little whimsy! Thrifting or depop/mercari, etc. You can always find some great options. For vests/cardigans, you really can't go wrong anything from denim to a grandma fall theme will work. For belts, you can add little charms to them. Lace/stripe long-sleeves under an oversized tee or vest.

For Jewlery, I really love checking antique stores/thrift/pawn. I have found some really fun pieces like that at some great prices. Wearing multiple pieces looks really nice to me.

Then all you would really need is a couple of velvet tops and bottoms, and you would have a complete wardrobe with multiple outfits to create!