I play the market a lot , i actually trade more than i play , don't ask me why but it is the part of the game that grabs me.
It is very tricky just now with the market falling so much so i have been mostly trading IF cards as they are always limited supply. When these card rushes come there is several ways to do it with normal cards, you can buy cards and try for insta-profit by listing for 1 hr straight away at small profits and keep relisting until they sell.
The other thing is if good cards plummet during happy hours etc is i buy them and sit on them for a few days until it recovers , i find listing on a friday night / sunday the best. Be aware though as it's christmas time EA will be spamming us with pack offers.
There will be plenty better traders than me but i bought the superdeluxe edition and bought 12k fifa points at the very start of the game , the only "good" card i have had all year is Hazard who i sold for 160k approx
This is my current squad so it shows you trading can be done, im pretty busy in IRL so am by no means a "hardcore trader" who puts lots of hours in alll the time (i trade while watching a movie with family etc) and as i say there will be plenty people who make waaaaay more than i ever could: