I am doing the same thing. My mother provided me a gift deed. Besides the deed I am attaching the following
1) My bank statement showing that I received the money.
2) An official letter from my bank that contains my account summary (the date the account was opened, 6 months balance, if there are any dues, etc)
3) A screenshot of the wire transfer that contains the unique transaction number (if your mom if transferring the funds via cheque, then take a scan of the cheque before submitting it).
It always helps to show the flow of money as it makes the process transparent.
4) An LOE explaining that I received my funds from my mother and details of both of our bank accounts. I'd really recommend attaching this LOE with all other financial documents, rather than in the seperate optional section as it would be easier for the immigration officer to track everything if its all in one place.
Hope this helps! If you have any more questions please feel free to reach out. I'm sure there are other ways of doing this but this is what I have done with my application.