You will actually pay much less tax than Warren previously estimated.  As you mentioned you will be receiving the Guaranteed Income Supplement (GIS), we can see that you are also eligible for the Age Amount credit.  (Plus your income from that GIS is not taxable).

So using the upcoming 2019 rates one can estimate on a taxable income of $23,064 in B.C., you would pay around $900.00.

However, the entire amount you will receive is not taxable, so the amount you are going to pay is going to be even lower than that amount. 

THIS IS AN ESTIMATE ONLY. If you are receiving around $900.00 monthly for your CPP benefits, combined with your OAS, you would have roughly $18,050 in taxable income and in B.C. you would pay roughly around $130.00 on your 2019 tax return. 

Here's a handy table from TaxTips.ca showing the 2019 Federal & Provincial tax credit rates. 

https://www.taxtips.ca/nrcredits/tax-credits-2019-base.htm

You'll need to fill out your taxes with all relevant information to get the proper amount owed. As an estimate BC has a personal amount of 10,412 and the federal personal amount is $11,809. Your income would fall into the lowest tax bracket of 5.06% in BC and 15% federally.

Approximate tax owed would be:

(23064-10412)*0.0506 + (23064-11809)*0.15 =    $2,328.44