If I have invented something, how can I get it patented and represent it at world level?

Similar to some of the previous answers, a PCT application is your best option and best "bang for your buck" for worldwide protection. Although it is more expensive than a national filing, a PCT application will grant you initial protection in up to 148 countries. However, you will need to eventually file for specific country/region protection no later than 30 months after the earliest filing date of your initial application.

I would add to the two previous comments that filing a national patent followed by a PCT is also a smart way to postpone costs.

As a rule of thumb, filing a patent in major countries (think USA, EU, China, Japan) will cost roughly 4-6k.

If you file a bunch of patents right from the start, you will have to pay that for each country. If you fils a PCT, the deadline for that payment is postponed by approx 30 months, which gives you more time to find additional investors in your idea.

Hi,
Here is a brief answer to your question, which cannot be a full legal advise. For further information, a patent agent/attorney should be consulted.

As you have already found out, patent protection works on a national or regional level. A patent is a temporal monoply given to the inventor/applicant by the respective jurisdiction, i.e. single nations. Thus, protection will always be on a national level.

(International) patent applications in a nutshell:
you can apply for a patent at an international organization: WIPO (www.wipo.int). Such international patent application can later be "converted" into one or more national/reginoal applications. The grant of a patent will then be on a national/regional level though. Optionally, you start with a national application and within 12 month you can file another application claiming the priority of the first one. This second application can be any national, regional or even internation application. In the meantime you may have received search results for prior art regarding the first application, which helps you deciding to continue and where.
As I said, it is a complex system, so the above is only a brief overview.

Oliver

As Oliver has basically noted, there is no such thing as a Global or International Patent - patents are territorial for each country. You can effectively get patent approval for a region - for example, if you file a patent application with the European Patent Office - but the ultimate patents will be for countries that you select. Normally, one files a patent application in their own country, and then within one year they file a PCT application - then, within, usually, 30 months from the date of filing of the original country application, you have to select countries or regions where you want to further prosecute applications in order to obtain patents in as many countries as you want or can afford - it can easily become a very expensive process, particularly since many countries charge annuities while the applications are pending or after the patents are granted.