Having watched pretty much every one of Gore's pro games, I'll try to shed some light on Gore's game and what he should be able to produce this coming year.
While Gore is short and stocky, he's not truly a power back. He will run over DBs who don't get good tackling position on him, but he won't move piles at the LOS. He uses patience and vision to find creases in the line and accelerates through them. If no crease develops, he won't try to get creative and bounce it out (he doesn't have the speed to do so), he'll just dive through a hole to try to get positive yardage. Running between the tackles, Gore is great at not losing yards. Gore is not an East-West, one-cut runner. He's most effective running between the tackles, but will occasionally explode outside the tackle if the tackle collapses the end.
So, the net is that don't expect Gore to move piles at 4th and goal at the 1, or to run sweeps. He's better 3-6 yards out where the OL has some ability to create creases. If Gase runs Gore sideline to sideline, he will not have success.
At the other end of the spectrum, Gore has never had great speed, but he has lost a step. He relies on good downfield blocking to break off big runs, and he has great ability to use downfield blocking. When he gets a crease--and he doesn't need much of one--he's still explosive and will gash defenses for 5-10 yards, but if he doesn't have downfield blocking, he's not going to get many 15+ runs.
How does this all translate to what Gore did over the past 2 years? At the outset, it is important to note that Gore was never unseeded by any other RBs. No one they brought in was able to perform better than Gore in the Colts offense. That said, Gore's YPC was the lowest of his career. Why? Many reasons: (1) the Colts had very predictable playcalling. There is an article out there that broke down their play calling and noted that in certain formations, the Colts ran running plays 100% of the time. If a beat writer recognized that, you can bet NFL defenses did too. (2) with a revolving door at QB, most defenses were able to focus on the RB play. (3) the Colts interior line was bad. So many plays, DL and LBs went unblocked. Forcing Gore to simply dive and get no yards. Mack -- Gore's back up -- had the speed to bust some of those same plays for big yards (see 49er game last year) -- but Gore can't do that. (4) The Colts downfield blocking was from average to poor. WRs TY Hilton and Dorsett are terrible blockers. Moncrief was better, but inconsistent. And, once again, the Colts OL was below avg in getting to the second level to set blocks.
Despite the challenges Gore encountered in the Colts' offense, and his career low YPC numbers, many Colts fans consider Gore among their all time favorites. He's a grinder that runs hard all the time.
I think a lot of knowledgeable fans recognize that even a great back won't produce with a spotty offense, OL and playcalling...e.g., in 2016, Gurley had a 3.2 YPC avg on the season. Gore no longer has Gurley's skills at this stage of his career, but in a better offense he could have produced at a much higher level. I think he's still capable of running for 4.2 ypc+, but it won't be the result of 3-4 40+ yard runs, mixed in with a bunch of losses. It will come from a balance of 6-10 yard runs with some 1-2 yard short yardage dives and the occasional 15+ yard run. He'll move the chains and set up short yardage early down situations for the offense, both running and catching the ball. For an OC, Gore is a dream because he can play every down (great blocker as well), and he gets out of a play what it is designed to do...what he wont get you is the jaw-dropping one off plays that CJ, Charles, or McCoy gets you 3-4 times per season.
