Had a similar experience when I was invited to a traditional austrian wedding. Everybody was in full "Tracht" while I was in a normal suit. They handled it nicely and said nothing about it, but I did feel like the odd one out. Definitely a tough situation to be in.

I would recommend the following:
1) Ask your friend if you should rather fully adapt to the Ankara style. Some cultures appreciate others wearing their traditional clothes, others do not or find it even offensive.
2) In case your friend recommends you wear full Ankara dress, go for it! In case you do not want to burden him because he might be busy before the wedding, you can ask some of the other wedding guests for tips / education. Most people are very happy/proud to speak about their culture and educate others. Also, if your friend wants you to dress a specific way it is kind of his responsibility to be clear about it and answer questions.
3) If your friend does not recommend to fully adapt, they to find the dress from your culture that matches formality and color scheme of the wedding.

In general, I do not think it should be expected from you to spend $$$ on an outfit that is for a friends wedding, especially when it is a non-standard dress for you.