If you did a "Factory Reset" on the device, it is extremely likely that you won't be able to get anything back. That is part of the point of a "Factory Reset" and also the "Hard Reset". To wipe data from the device.
Now if you had the phone synced to a google account, and had updated it regularly, then you may find your files there. If not, well you can try the following info to see if it helps, but I will be honest with you and say the odds are slim to none.
There are a few apps/programs out there that 'may' be able to help you recover the data.
A few of the programs you could try would be... DiskDigger, MobiSaver, Android-Recovery and Tenorshare. They are all data recovery apps/programs. There are many others out there, so check around and see which you would rather try. There is also one called RECUVA, that I have heard is free, which you could try.
One important note though, most of these programs are not free. They may say they are "free" or have "Free Trials" and "Free Downloads". Yet to actually recover your data, and get your files back, you may be have to purchase the program/app. Just so you know.
NOTE: For future reference, I really would suggest backing up your data to a computer or cloud. Often. Better to spend the time doing that, rather than to be out all that stuff if the phone dies, things get deleted/erased or it gets stolen.