Second do more chores around the house and help out your mom
Third give your mom some compliments.
Next buy your mom some chocolate.
Give her a fresh morning with breakfast in bed
Help her with the groceries or cooking
or
Tell her how the thing you want to buy helps you like all the positives and hiding the negatives
Throw her a suprise party or give her a special treat.
And for the final touch ask her to buy you what you want from ebay.
Make your mom breakfast in bed.