If you want a challenge then go Owner mode with Jacksonville. Draft as realistic as possible. Cut your dead weight and watch your funds when/if you sign FA's.
In my 3rd year, I'm almost a playoff team. But I went 4-12 my first year, 2-14 my 2nd year, and 3rd year i'm 9-7. Started winning games but wasn't quite there.
Jacksonville is TOUGH to play as OWNER mode. If you don't watch your funds, you'll go broke and won't be able to sign players. Coach mode is very easy and is nothing like owner mode.
With Jacksonville, it's not like other teams where you have "some pieces" in place to build upon. Nope, with Jax you have to practically rebuild the entire team. Your entire OL sucks. Your WR (except Blackmon) suck. Your RB's are mediocre. Your DL is below average and your entire secondary blows badly.
The only good players on your team are:
ROLB - Telvin Smith
MLB - Paul Posluszny
That's it. Oh your Fullback is above average but nothing incredibly special.
And Bortles is horrible at first, and you have to develop him. Not just play him, you need to DEVELOP him using the XP Game Prep. Get him to SuperStar and then start dumping points into him. He will come around.
The good news is Paul Posluszny will get you 150+ tackles a year. In fact, he led the lead in tackles two years in a row for me. I sim every regular season game except week 1 and week 4. The rest are simmed. Makes it more realistic stats wise and the seasons go by faster. If I make the playoffs, I sim them except the Super Bowl. I'll play that.
Good luck