I finally managed to get a credit card after 3 rejections due to lack of history. To be more specific, I went to my bank and applied for one... they have had my checking account for a while so I figured my best chances are there.

So after a month later, I got a Visa card with $500 credit limit and the outrageous 23% APR.

I've used it about 10 times by now within the last 3 months and paid in full and always on time for every statement. About when should I ask for a credit limit increase and lower APR?

That is good. The 23% APR does not matter because you are paying in full each month. I would say wait for 6 months to ask for credit limit increase and APR decrease. Also, you may want to obtain a store card to further build your credit history. If you keep on paying ontime you should be on your way to building a solid credit history.

Thanks Colin.

About the store card, it was infact, one of my 3 rejections when I applied for a card before this.

I tried for a GapCard but was rejected due to lack of history. Do I have a much better chance now?

I would say you should wait a bit. When you are turned down for a card your credit rating can be negatively impacted. If you build up a longer history with your current card and let more time pass between your string of turned down applications you will have a better chance.