You need to decide what you want as quality is personal and subjective. As a breeder breeding to an established standard and competing in shows, my quality is going to be beyond what most care to consider. Review the discussion here recently on evaluating a crown tail. Owing a show quality fish or even breeding it is not necessarily better if you have no desire to continue to produce a quality line of fish or show. It is not like a show quality dog.
If you want to just breed some fish you find attractive then purchase what you like and breed healthy fish.
If you want to be a bit more of a serious breeder, first place to go is the IBC and join. The site is a bit awkward right now but it is being reworked. Once you join you have access to the standards and the top breeders in the hobby. The standards are necessary as you need to understand the colors and faults. Hard to breed quality if you do not know what it is.
Then you have to learn to recognize that quality the standard is looking for. This place is educational.. but if you want more, many of the top breeders have FB pages geared to producing quality fish and helping others in the hobby. My page is much bigger than I ever imagined it would be. Aside from a few crazy cat antics, I try to educate people on form and the standards. I'm a bit pinched for time here lately, but I try to regularly feature quality fish and review the better ones for good and bad points offered on AB. I also have a site and forum that has general questions, but also tends to have a bit more info directed at the more serious breeder.
As you learn about the standards and get the desire to produce really good fish and want to show.. then you tend to establish relationships with a more experienced breeder that can help you along. I have a few I am mentoring towards the show ring. So there is the even more in depth discussions on quality.
Realize anything you buy is a cull. You just have to find a breeder that has some of the better culls around. Few breeders will show their breeder quality fish let alone offer them for sale. If you get lucky you get the "B" string that are show quality. Most often you get the "C" string. Here are some of my recent culls [ "C" string] offered for sale. I have not produce enough males to show let alone offer for sale.. so I tend to offer females..
Most do not have their top quality this good... and this quality may not be what you need or even want. So advice is.. read, join some forums where the breeders frequent and ask questions and learn. If still really interested join the IBC and get help selecting your breeders. Then good luck and hope to see your fish at the shows.