What you're really trying to do is locate the latest cards put on auction by searching for the most recent cards in ascending order, and filtering it through teams or positions, so you can see cards that are currently to auction. When you search this way you might be able to "snipe" cards which have been offered to auction for sale at a cost much lower than the worth Mut 25 coins when the bidder is swift (and fortunate) enough. However, in any case, you'll be able to discover the lowest cost for the card you're looking for.
If you happen to come across the types of legendary snipes that can lead you to purchase cards at much less than they are value, you might think about "flipping" these cards by offering them for auction for a more normal cost (this is where the Buy Now filter can come handy in determining what people are prepared to for) and thereby helping make money from the transactions which you can then be used for other purchases. Rinse and repeat, and you will see your money making money.
Missions are brand new to MUT for the year ahead, and though some appear like a few reminders of all that you can accomplish in the MUT mode (and may be more clear on what you'll get upon completion) There are other missions which can offer decent rewards for achieving achievable goals.
The easiest is likely the daily challenge of the "cheap madden coins Dedication" series that will require you to win two games, and then purchase one of the packs at the shop. As we've discovered that buying packs from the stores isn't a good idea I'd recommend you purchase the most affordable pack available (the Buy a Player pack for 500 coins) to complete all the goals. The weekly goals will also offer at least a few tasks you can accomplish without much commitment, and will provide you with additional coins to deposit into your savings account.