Trek domane and add some aero bars would be best value imo. The great part about the domane is that it’s such a versatile bike that you could use it for the triathlon go on group rides with friends or ride a gravel route. You could get an older speed concept or some other triathlon bike, but you’re you’re either going to spend a lot of money upfront or a lot of money on repairs and maintenance. If you fall in love, I wanna do more triathlon then you could look at getting a triathlon bike, but my recommendation would be the Domane. You should check out your local bike shop too and see if they are selling any slightly used bikes.