Flipping on the market is pretty easy once you learn prices and how it works. I came from playing Madden and 2K and the market is a lot different as it doesn't have capped prices on items. I always look for a margin that will be bigger than 10% because of tax. Anything that can make you 250+ stubs is a W in my book. Even ones a little smaller is good because if you do a lot of them over and over you can make some really good money.

I mainly stuck to diamond perks, gold perks, diamond equipment and the topps now series. This will change here and there depending on what they release but you can always flip cards. Silvers are good as well to start and even gold cards. I'm no pro on this but I finished the AL in 3 days of flipping and then the NL collections in the next 3-4 days. I have chipper jones as a no money spent player basically. It's very confusing at first and it seems a little unmotivating considering you're probably only going to be getting 250-750 stubs a flip but it's very much worth it once you notice how much you make in an hour, 2 hours, a day etc.

Here is a video explaining essentially what I did, I took a break since I got chipper but this guy is a very good youtuber for the show and I suggest watching this all the way through to get the jist of it all.