If you're ready to move on from the free version, you would want the Standard Licence; if you look at the comparison of the different versions on the purchasing page you'll notice that the Standard and Business licences have exactly the same features -- you only need the business licence rather than the standard if you have made more than $5000 with your Construct projects, at which point you can easily afford to upgrade.
If you're still young, you should probably discuss the purchase with your parents, and show them the purchasing page with the comparison of the products as well as some of the cool games you've already been able to make.
Hope that helps! <img src="smileys/smiley1.gif" border="0" align="middle">