When you are looking at using free Drupal themes, you have to think of the disadvantages. The main one is that there will be thousands of other websites that are using the templates. Your website will not be as unique as you want it to be.
The only way to gain a unique design is to change something about the theme but this can cost a lot of money and you could be waiting a long time for someone to do it for you. If you want to do it yourself, you will need to know a little about the design and coding.
You could struggle to find a design that you have in mind depending on what your website is for. The themes are made based on what most people want a website for but if you are looking for a completely different idea then you will need to look into creating your own or spending money on the other Drupal themes that are available.