Interesting debate.
The beauty of this game and frustration is that there are multiple ways to approach the game, and multiple layers to delve into. It's like super-giant massive labyrinth which has no centre point and hundreds of people milling around looking for little hidden 'easter eggs'.
Basically, have a philosophy. Run focused, Pass focused or Balanced. Then decide do you want to be possession based, clock control or quick strike. Conservative or aggressive. Do you want your D to be bend don't break, blitz heavy, man to man, do you want to force errors.
Are you patient or impatient. Patient owners will be more draft focused and build slowly. People like me will prioritise free agency and trading, building for the here and now.
What do you want from a player - Players with good fundamentals (speed, acceleration, strength) these tend to be players with great versatility, who can cover multiple positions. Or do you want technicians who can fill specific spots - you'll need both - preferably players that have both.
Everything else comes from experience and effort - the more you put in, the more you get back. The deeper you look, the more Easter eggs you'll find.
If you want 5 things that will help
1. Get a good QB - pass accuracy, field of vision and intelligence all need to be 80+ rated. The rest you can work with. A QB rated less than 60 in accuracy and field of vision will barely complete a pass, except to an opposing defender.
2. Speed kills - more than that 'fundamentals' kill - Speed/Acceleration/Strength are (at present) dominant factors
3. Always, always, always have a punter and a kicker on your roster - both need to be rated at 80+ in strength, accuracy (and for a Punter) timing. Without a good kicker and a good punter you are going to lose more games than you win
4. Set yourself goals - win a game, post a winning record, post a shutout, win games from more than 10 points behind, make the playoffs, win a division, win a Conference, win the big one, eat, sleep, repeat.
5. Don't sleep on Special teams - Long Snapper, Kick Holder, Punt/Kick returner, Gunners, Rushers, Blockers, Kicker, Punter - all should be on your radar for late round draft picks and free agency.
6. Don't stop looking for something to improve and most importantly have fun.