I did have some "goal clothes".
I didn't go out and buy something too small - and I don't recommend it, either, because your shape might well change, and something that you think will fit might not - but I had a gorgeous pair of purple jeans that I'd saved from when I used to fit in them.
I loved those jeans.
So they were a really good goal to aim for.
But then I slimmed past them and had to give them away!
I did have another goal though: there was a brand of clothes (Desigual) that I absolutely loved, but couldn't wear, because they don't do big sizes, and they come up really small anyway.
So, although I didn't go out and buy anything from them, I kept going into the shop, and reminding myself how gorgeous their stuff was, and promising myself something as soon as I was at target.
Which I just bought, last week!
So I'd say, if you haven't got anything of your own in your goal size - don't buy, but look, and make a promise to yourself to buy when it fits. That's good motivation.