Thanks a lot for the reply. I will be living a very normal lifestyle. I won't smoke and drink as well.
My plan is like below:
1500-2000zl for rent
1000 for food/grocery
Is that fine?
Is heath insurance NFZ mandatory? Because my employer is providing medical insurance for some money.
Finally, as my wife won't be working. Can I declare join tax declaration? If so, then how the tax will be calculated.
You should plan for rent being at the top end of that range, but utilities being lower. The rest is doable, however food might be a little more, depending on how you live. Some items will be cheaper than you expect, and some things will be dearer. Biedronka (a supermarket chain) is a good place to shop - it isn't expensive and the quality is good.
You'll need to pay ZUS (social and health insurance) if you're on a normal contract of employment. Use this tool to calculate the difference between gross and net salary (you'll probably need to put it through google translate:
Aboout your wife's tax allowance, you should check with colleagues who have foreign spouses when it's time to make your annual tax return, however your HR department will deduct the normal tax from the start.