There’s a huge range of geometric compasses available costing anything from one or two pounds to £50 or more. Some really cheap compasses are a complete waste of time, as they are too loose to draw a perfect circle. You’ll just end up getting extremely frustrated. I use this Faber-Castell compass for drawing my mandalas. If it is out of your price range then please do read my blog post with further recommendations and tips on what to look out for when buying a compass.