Buying and affairs arrangement relies mostly on luck. You charge to actuate your bulk point because there are a bulk of variables that appear into play here: accumulation margin, time, and accessible pile/transfer account size. You need to find a profit margin that makes you the most amount of money. While you can try to sell at 100 coins more than you bought at, it may be difficult to keep up for long enough to make it noticeably profitable because your available space for these cards will keep filling up. So keep on the lookout for cards that you can resell for 200-300 more. As a rule of thumb, you should try to get as close to doubling what you spent as possible.
Believe it or not, this is actually really easy to accomplish. You can expect to purchase contract cards for all 40 slots in your transfer list in a decent amount of time, although it may take a while for them to actually sell. However, the problem here is that after 40 slots, you’re done. You can, for example, spend 8000 FIFA 15 coins on 40 contract cards at 200 a piece and resell them for 450 each. Although you’ve more than doubled what you spent with a nice profit of 10000 coins, this isn’t exactly a quick turnover. If you get advantageous you will buy fast and advertise fast, but there is absolutely no calibration to this adjustment — as you achieve added bill you cannot apprehend to use your added spending ability to achieve more.