The GTX 1050 itself only requires 75w but Nvidia recommend you system have at least 300w for the entire system. I would personally recommend a 500w power supply for your build because they are relativity cheap and it'll give you room to upgrade. As for which brand to buy, seasonic and coolermaster generally make the best power supply's in my expirience. If you are unsure of how much power your system needs and want to know for sure the website pcpartpicker (https://pcpartpicker.com) will let you enter all the parts of your build in and tell you how much power you need.
tldr; Buy a 500w seasonic or cooler master power supply.