Well, who is topping the sale barn near you and do they sell replacements? That's as good a place as any to start i suppose. Find the cattle you like nearest you and see if your environment can replicate their results.
I am not saying you need to spend a lifetime making the perfect herd, but if you're spending time and money and energy to create a herd that makes you money, it does take years of selecting for traits. You can't just buy someone's cows and have the worlds best herd. That's the joy of genetics, if there was a perfect cow or bull that was able to identically replace itself in every calf, we wouldn't ever need to have these discussions. Heritability of traits have both positive and negative outcomes and someone else said that crossbreeding can help with that and they're right. What I'm saying when I talk about handing it to the kids is by the time they're old enough, you'll have spent 20 years selecting for positive traits and should have a cow herd that is pretty solid and lacking in genetic issues. The worlds best bull can not do this in one year or even five years, that's my argument, it's a life long journey. Starting with awesome cattle makes things easier and using good bulls helps but it takes years of trait selection and selecting the right animals for the environment... not every animal performs the same on the same grass. Program evaluation of inputs to outputs to outcomes and then ensuring that your goals are being met? That's a lengthy process and requires constant re-evaluation