English language test (TOEFL or IELTS or something else)

I’m thinking of learning for an English language test. I haven’t got any special goal so far. I’m learning English just for fun. Nevertheless I’d like to know how good or how bad my English skills are.
I’m not sure which test I should choose and which school is the best.
I’ve heard about TOEFLl and IELTS so far. Is anybody a little bit better informed than me? Has anybody experience with this issue? Can I learn online? How much does it cost?..
I appreciate your help.