I recommend that you take note of your size by trying a friends boots or a local supplier first if possible, if not then try to get your boot online from someone who offers exchangeing so you can get the best size.
Hi Faris! In my opinion you shouldn't buy your very first tall boots online. You should go to a tack shop and try different ones and see how they fit you and whether you like them or not because if the ones you buy online don't fit or are too big, you will end up spending more money unnecessarily.
Hope I helped you.