Do I need all Domain Extensions

These days there are hundreds of domain extensions, so unless you’re Amazon with an unlimited budget, I would suggest only the top level domains – .com or .co.uk.

The .com and .co.uk extensions are known as the Top Level Domains (TLD).  If either of these two are available for your chosen name then it’s likely your name is quite unique.  If not then I would assume there is already a website/business on one of these domains and therefore purchasing the .net or other extension is not going to be worthwhile as it will be difficult to get above existing websites using those domains.