Church Donation - Do I give?

I've been attending the church here for some time and each time they pass the "red bag" around (see video), I tend to feel a little uncomfortable. It could be because when my friend brought me there some time back, she told me that normally, everyone gives something, no matter how small. Since she has gone back to China, I have been going to church on my own... and I am kind of at a lost as to how much to give.

Usually I give two dollars or so but today I realized that I did not have any small change and I gave a five dollar note. While the giving has never been an issue for me, five dollars is quite a big sum for me. Some friends tell me they normally give about 10% of their salary. This means about SGD95 for me each month and this can be quite painful on my wallet.... especially when every month, my finance is so tight and I am sending almost every dollar I earn back home.

Some people tell me that the more you give, the more you are blessed! Is this true?

Is giving a norm in church? Is 10% too much, too little? I really have a lot of questions and I hope some readers can enlighten me.