This is a strategic business decision: In which countries do you intend to sell your products/services and thus where will you use your trademark? Your country, Europe, several countries at once… You decide!
Registering a trademark costs time, research and money. If your business plan is mainly local, starting in your own country should be enough.
On the other hand, if you know you’ll grow fast and across borders, your research time and investments will increase too. In this case, we highly recommend consulting a specialist in trademark law to get advice on the best strategy of when and where you should register.