If you can avoid ever having a credit card, do so. $50 isn't worth the hassle of working out how to cancel it and prevent any charges. I've seen people whose lives have gone down the toilet because they treated their credit card like free money and bought more than they could afford. You should only ever get a credit card if you really need it and have researched thoroughly to get the best deal. I got my first one when I got my first full time job, and I needed to be able to get to work more reliably than the bus, and I needed it to buy my first motorcycle. But I worked out my how much I could pay back per week and which bank would give me the best deal on terms of interest rate and monthly fees so I would have to pay the least possible overall. You may find you need one to buy a car (if you find a rate cheaper than a car loan) or for holidays because you get a good deal on international purchases. But don't get one just for fun. There's a reason they are giving away $50, and it's because it's a crap deal for you and they are likely to make much more out of you. At least research thoroughly first.
So you took a credit card out for a motorcycle loan? Maybe they do things differently in Australia, but in America, that's just a bank loan.
Someone else also mentioned never get a CC, how do you expect to build your credit if you don't have one? As long as you carry a low balance and pay it off in full every month, interest will be avoided.
I have 5 CC and this is how I work them and pay them off in full every month.
BOA card - never use, has no benefit, it's there if I'm in al jam.
BOA Cash back - grocery shopping, fuel, etc. I get cashback on every purchase.
AMEX - Household bills, power, water, gas, car payment etc all goes to this card, I get points which I turn in for gift cards.
Home Depot - great to have if you need a major appliance, if I spend $300 or more, I have 6 months interest free to pay it off.
Synergy ( i think it's called ) - My bed, came as a CC for the account, can use it in limited places.
I pay my bill in full every month other than the no interest cards for xxx amount of time.
My credit is outstanding, never require a cosigner and can purchase just about whatever I want.
Bottom line, Credit is simple, don't abuse it and you will be fine. Anyone telling you otherwise, abused it and caused their own financial issues.