Applying for IELTS you need to prove your English language capability to apply for your Master's course in Germany. You can prove it by giving an IELTS examination. IELTS and TOEFL are two widely accepted international standardized English language tests. In the event that you also want to apply in any other US university, TOEFL could be a good decision. In almost all the German University IELTS test score is accepted with the same section and similar testing styles. MOKSH recommend you to select IELTS as it is a better option.
Now IELTS is freely available online so self-study with some dedication should get you through this. MOKSH suggest you not to get lost in all the courses. Pick one or two from each category and stick to them.