In addition to the gacha card pack system and purchasing players with fame, you also have a chance once per day to spin the Wheel of Football. This is a randomised prize wheel with players of three different star ratings including a five-star player, plus equipment of varying rareness.
Rarer equipment items have a small chance of coming up on the first wheel spin, but as each of the fifteen options on the wheel is won, its tickets are taken out of the virtual raffle which means the probability of the remaining rarer resources coming up on the next spin increases. As you keep spinning, even if you start off collecting common prizes, enough options are taken off the wheel that all you are left with is rare prizes.
The first spin only costs credits, and you may be happy only to spin once per day. If you want to go for the big prizes with greater odds, you must keep spinning by using rubies.