1) Make sure it's an Intel CPU and not AMD. A decade ago, AMD was great but they have fallen far behind. Intel will run a lot cooler which means fans don't have to run as hard and the noise difference is noticeable.
2) Stretch the budget to get at least a 128GB or preferable a 256GB SSD. Buying a cheap laptop is fine as any CPU can handle the light load you are proposing, but the difference in boot and program load times can be 10 or 15x faster (seriously, not % faster X faster). It makes an old slow desktop or laptop feel fresh and new.
3) Make sure the screen is at least 1920 x 1080 - or full HD 1080p. Lower res is really bad particularly if you want to watch movies and more than 1080p is still kind of waste because you can't find content beyond 1080p (caveat, I'm not a Netflix user, so I don't know if they have added 4k content). Based on the budget, I wouldn't reach for 4k.
Follow 1, 2 & 3 and then find the largest screen that fits your budget. It will come with Windows 8.1 which is fine. If you hate it, you can buy an addon called Start8 for $5 and it makes it exactly like Windows 7. You will also get a free upgrade to Windows 10 when it comes out later this year and that will basically be the best mix of Windows 7 & Windows 8 with additional features added on.
Hope that helps.