As said by most people here, a duel core processor is enough for what you need. The G3258 is a decent two core processor at an affordable price and would suit all of your needs you have stated here. If you open a lot of programs you may get lag with a duel core, just make sure you have enough memory and you will be fine.
I used to have a laptop with an Intel Celeron, 1MB L3 Cache, 2.2Ghz and only one core, I was pretty much fine although all I did was watch youtube video and use the internet, if you're going to be streaming HD videos on Netflix however then look a little higher although my celeron did me well.