Since you are earning less than RM30K currently, you can't qualify yet for the FREE FOR LIFE Maybankard 2 Cards.
Click here to my article The Best Credit Card Combination 2014 where I prepared a table of comparison between cash back cards.
IF you do spend RM500 a month on petrol or groceries or dining (pick 2 out of 3), then the HLB WISE credit card will earn you most in cash back BUT only the first year annual fee is waived.
For petrol, if you pump less than RM300, then the UOB may be good for you where you can earn 5% cash back or MAXIMUM cash back of RM15/month. And if you can pump at BHP, you get extra 2% $MARTCASH. First year is FREE, subsequent years they do have auto annual fee waiver if you swipe 60 times a year (which works out to be 5 times a month). But you can request for annual fee waiver and the chance of getting it pretty good.
Now, since you are only earning about RM2K/month, I strongly suggest you do not give your mum a supp card or to anyone because if they were to max out your credit limit, you may be in debt and it is not good for a young person. I am not implying that your mum will max out your credit card, it may be she lost her supp card and someone go charge the card and she failed to inform you in time and the bank will say you are liable for the charges, better to be safe than sorry, i.e. be kiasu.
Since you new to credit card,
click here to my Tutorial Page and read my article especially CC101 and Credit Card Interest Rates.
Once your annual income touches RM30K, go apply for the FREE FOR LIFE Maybankard 2 Cards.