My parents won't let me have a good quality skateboard even though I have one now it is too big for me and it's from toysrus so there is no concave bad quality wood and plastic trucks what to do?

Even though it may not be the best, try YOUR best to make use of it, and to have fun with it. See if you can develop the skills to overcome some of the shortcomings of the board. This way you'll show your parents that you are serious about skateboarding and are willing to work at it. Also, start saving money either to buy one for yourself, or to contribute toward one with your parents' help. They did their best and they spent money on the board you have (I'm presuming) and most parents don't have money to spend on something they thought they already took care of. Be considerate and show them what you're made of. You'll find that when you do get a good quality board, you'll be better at it than you can imagine, because of the effort you'll put in.