Welcome to CruzeTalk.
First, download the 2014/2015/2016 Limited owners manual from
Chevrolet Cars, Trucks, SUVs, Crossovers and Vans and then look at the severe service schedule. At a minimum I would change the oil & filter, spark plugs, gear oil, and brake/clutch fluid and adjust the rear brake drums. The 2011 manual is lousy for routine maintenance. If you've done any of the above, kudos and keep up the schedule maintenance.
Oil & filter - dexos1 or better oil. Do not let your OLM drop below 30%. GM changed the algorithm in 2013 to provide a more realistic report on the OLM. Many members here use a full synthetic oil vs. the semi-synthetic dexos1 standard.
Spark plugs - we know for a fact that the spark plugs coming from the factory were very inconsistently gapped. I'd put in a set of NGK BRK8EIX plugs (assuming you don't want to do this very often) or NGK BRK7EX plugs if you don't mind changing the plugs every 15K miles or so. The BRK8EIX should last 40 to 60 thousand miles depending on how you drive. Be aware, however, that pulling the ignition rail off is tricky to do and you need to be careful to avoid damaging the boots. A replacement rail is $80-90 at Amazon.com.
Gear oil - I recommend swapping out for 2.5 qts of AMSOil Synchromesh. The spec for the fill level was recently changed from 2 qts to 2.5 qts. The GM gear oil is only good for about 15K miles. The AMSOil synchromesh will last for 45K and has eliminated the 1->2 WOT grind that I had.
Brake/Clutch hydraulic fluid - change every 30K or 40K (I don't remember what the 2014 manual says).
Rear Brakes - not properly adjusted from the factory. I suspect this should have been a dealer prep item that got left off the list. Basically, if you pull your hand brake up it should stop about half an inch in front of the center armrest when it's extended forward and the rear brakes alone should hold your car on a hill. The 1.4T engine is simply too small to hold the Cruze on a hill.
Definitely poke around here and don't be shy about asking questions or helping other members.
Finally, give 91 octane a shot - your car's engine is actually designed for 91 octane (look for KRD on the glovebox label).