Currently, i make 4000zl NET in a tiny town.
Taking in cost of living, that's much better than you can expect to do in Wrocław, and probably the best you could do anywhere in Poland. Like I said, if there is anyplace in Poland where money is to be made, it's off the beaten track in small towns where no foreigners go. No competition.
For cries ache, stay where you are and spend your time building up a decent clientele.
How will it not be possible to make more in a big city like Wroclaw?
Wrocław is one of the most attractive cities to live in in Poland, and, consequently, one of the most expensive. It draws scads of British and Irish slackers and backpackers who are desperate enough to give "conversation lessons" for as little as 20 PLN an hour. No school in Wrocław is going to agree to give you 40 hours a week. You would be lucky to get 20, and even then, you would probably have to work for several schools.
Also, don't forget Wrocław is a bit larger than the small town you are in, so getting from lesson to lesson can eat up a lot of your time.
By the way. I lived in Wrocław for eight years myself. Before that, I lived in a small town off the beaten track. Materially, I would have been better off in the small time if I had made my living solely by teaching.
There's a story (sounds apocryphal but apparently true) about someone advertising private lessons at 40zl a pop. She didn't get many takers and was short of money so she put the price up to 60zl and got a lot more enquiries...
That isn't going to happen unless you have serious qualifications, and it won't work for young teachers. Clients that go for this want to see a thick layer of coarse hair on your oversized balls. If you are not a genuine alpha male, forget about it.
I charged 70 PLN to a few select clients who were very reliable and gave me lots of hours per week in three hour blocks. More mentoring than teaching, though. Otherwise, I just didn't find it worth my time to deal with bit players. I made a lot more on translating and editing without the hassle of scrambling around town from client to client. For the universities, I charged 60 PLN because they were pretty reliable about paying me. Sometime a few months late, but I could count on getting paid eventually. But then, I have a research doctorate and a medical degree as well, so I was operating on a plane where I had no competition.