A few things ...
* The best decision we made in the first year of operation was buying a group of seven older cows (7yrs to 10yrs old) who were in their last trimester from a long-time breeder with a great reputation. They shot their calves out with no problems (despite the blizzard half of them were born in) and raised them all up to weaning. It's LOTS cheaper to learn on lesser expensive cattle than to learn on elite cattle.
* Once you have what you think is a reasonable handle on what you're doing (ranging from stockmanship to grazing to breeding ... etc ...), upgrade your cows ... sell / eat your oldies and plow the $$ into proven cows who are 3-5yrs of age with the best genetics you can find (and, who are proven in-calf, ideally with sexed heifer embryos in route). Ideally, every cow you get in this group will have had her 2nd calf before her 3rd birthday. In a perfect world, you will be able to get through two or three calving seasons before you have to figure out a way to coax a calf out of a heifer that doesn't want to let go. The increased confidence around your cattle will help this eventuality go as smoothly as it can go (which, sometimes isn't that smoothly). Also, by buying bred cows, you can take your time to learn about genetics, breeding, etc. and to find the people who have the genetics you think you want --- it takes time to do the research and the networking to actually locate the best of what you want.
* Fertility is the most important thing in your operation (roughly, research indicates its 10x more important than growth, and growth is 5x more important than carcass traits, when determining the profitability of a commercial operation). Fertility is a function of body condition. Smaller frame cows can stay in better condition in a rough environment (drought, etc.) than lanky cows.
* Cattle come with four rough measurements ... length, height, width and depth. All else being equal (temperament, price, genetics, etc.), I'd prefer long bodied, short-legged, wide and deep-gutted cattle over some of the frame-chaser cattle others prefer. To wit, I drove past a place close to me a couple of weeks ago and wondered why the owner had decided to put a horse out with all of his cattle ... only to take a second look and realize that the animal in question was no horse.
* Ask lots of questions and make your own decisions. I looked at black and red angus, galloway, tuli, senepol, south poll, limousin, and hereford before picking our direction.
* Travel around and see what other people are doing in terms of management, genetics, marketing, etc. There are some seriously smart and creative people out there. While one guy may have a very different bent than you, by knowing them, when you come across a problem that is right up their alley, they'll be more inclined to pitch-in to give you the benefit of their years of expertise and insight.
* Enthusiasm is required. As is patience.
* The best cattle in the worst breed (whatever that might be) are better than the average cattle in the best breed (whatever that might be).
* Understand the genetics behind how animals get fat (leptin, calpain, etc.) and research whether or not you think the butterfat and protein content of the cows you're looking at will impact the quality of the calves (I, personally, believe that understanding the kappa casein, beta casein and beta lactoglobulin genotype of your cattle will save you years of 'fixing' cattle that are poor doers).
I'm sure there is more ... but ... start small and start cheap ... learning on experienced cows that you couldn't screw up if you tried is a much better idea than trying to (say) learn on a group of high-dollar heifers.