A perfect dress exists for you, but it requires research. Check websites that have fitting engagement outfits and spend some time choosing an outfit that fits your event. Also, feel free to try various dresses. The best way to see if a dress suits your big day is by trying it on. Make sure your dress coordinates with your jewelry, makeup, and hair to prevent a last-minute scramble. While choosing your dress, ask your partner for their opinion to ensure it doesn't clash with their outfit.
You might have many options that you but involve experts who can help you best the best and most affordable advice for your dress. However, with that said and done (pun intended), remember this is YOUR day —make sure what you like, taste, want your style to be reflected on that day. Ensure you dress according to the weather and check the forecast before hand.
Enjoy selecting your dress, and have a fabulous day!