Spending Confustion

Good morning everyone, was hoping someone could clear up some madden cash questions for me. I did some looking into the sub and saw people suggesting that you pay for one stamina refill and one event stamina refill per day, to total 300. Which is then considered cheap because you get 200 back from completing the daily challenges.

However, wouldn't I need to still buy a pack from the store for like 50 madden cash to actually complete the daily challenges? If I'm spending 350 a day, getting back 200 it seems like I'd run out of funds pretty quick.

Additionally, should I not be targeting FP players? Since they are a high OVR I've been pouring everything into the last upgrade pack. This normally lets me get every single player for that month, and if I'm really committed one of their iconics.