If you're not a big fan of the online Madden community, fear not as this can be done reasonably easily solo. But there is a bit of a time investment involved.
First off, start yourself a Madden Ultimate Team with the starter pack provided. There are a couple of tasks indicated on the main MUT menu screen that can earn you some goodies. But what you really want to do is start with the Solo Challenges, in the Training Camp section. There are 33 games in this section, and they are really easy to win even with a bad team so cash in on those rewards - 1,000 coins each and a small pack of cards that includes a silver-calibre player.
Every time you break 7,500 coins you can buy a Pro Pack from the MUT store. If you get better players (including the training camp reward players), don't insert them into your lineup yet unless you're really struggling. You want to go to the
Adjust Lineup screen and press the
button to create a secondary lineup - name this something you'll remember to differentiate between the lineup you're playing all your solo challenges with (i.e.
Challenge) and this one that will just keep getting better until you hit the Achievement goal of 80 overall (i.e.
Achievement).
When you have your
Achievement lineup selected, use the Lineup Tools (
) to generate the best lineup (best overall). This will automatically slot in all the highest ranked players in your collection into the appropriate positions. Now switch back to your
Challenge lineup and go play some more Training Camp challenges. You probably won't hit 80 yet, but that's okay - there are plenty of other easy challenges left.
Once the Training Camp challenges are done, move on to the Regular Season challenges. There are eight for each team, and they start on Rookie difficulty progressing through to All-Pro. I'd recommend slogging through all the Rookie difficulty games first, and progress to higher difficulty as your skills get better (you may need to start beefing up your team a little bit here to stay competitive, but you probably have plenty of leftover good players here and there who aren't in your
Achievement lineup.
Keep swapping over to your
Achievement lineup as you get more card rewards, or more packs, and watch that overall ranking inch closer and closer to 80.
A note about contracts: If you see it take a step back, it could be that you've had one of those lineup players in your
Challenge lineup as well, and his contract has run out. No worries, you should have plenty of contracts available to get him back in the lineup. Save those contracts for your good players, don't spend them on the lower-tier bronze players. Instead, swap in another bronze player of comparable rating (or even lower if you're finding these challenges really easy) and burn through those players instead.
I hope this is easy enough to follow. If you're not clear on something, just ask in the comments and I'll try to clarify in the solution. Have fun! This mode can get ridiculously compelling to play once you get into it.