Yes it is only $300. But it is a 33% move. If you do it enough you can make some good money. I didn't say I was becoming a millionaire overnight. I am just making a 33% return on my investment, which if you ask me is not that bad.
How many shares are you trying to buy and at what price? Maybe try buying fewer shares. Are you using an all or none order? That could also hinder it from getting filled. I just put in an order to buy the quantity I wasn't and make it good til cancelled and it is normally filled within 2 days.