Never get a clear clue about drones and I just heard DJI is an outstanding brand in this field. So I just wonder if it needs a license to fly drones? And is it easy to fly Phantom 1 for rookies?

DJI are the market leader (by a long way) because their products are so good.
But the Phantom 1 is stone age and way, way behind the current technology.
If budget is an issue look at the Phantom 3 Advanced for the most drone for your dolllars.

Phantoms are much easier to fly than you imagine and that makes some beginners overconfident and get too adventurous too early.
There's a lot to learn to ensure that the things that could go wrong, don't.
You don't need a licence for recreational flying but there are rules.
Here's a good place to start for rules:  https://www.faa.gov/uas/getting_started/

DJI is the leader, but understand that if you have problems requiring customer service, you better have patience.  They are not known for superior Customer Service.  Some of the mods here, though, are a great source of information.  They do make a great drone, but setup can be confusing, there are constant updates (that don't always go well), and there are a lot of gotchas that can result in unexpected behavior or a crash.  Just flip through the threads on this forum to see the kinds of issues that operators are having.

That said, they are addictive.

They are not known for superior Customer Service.  
You are absolutely 110% right

You may want to start with some less expensive UAVs.  An example would be the Syma C5A or something like it.  That way, if you crash it doesn't cost too much.  When I was new to the hobby, those little drones got me past my initial fear and ineptitude so that when my P3P arrived, I was much better prepared.  No crashes yet!

Just got a DJI Phantom 3 Professional 3 weeks ago and it's absolutely awesome
Never flew a drone before but I got a hang of it pretty fast
It is so fun to fly it and with it's camera you can take some amazing shots
I've never crashed it myself but my friend and my dad did
Luckily the fix wasn't expensive
The Phantom 1 is not worth it because it's really old and doesn't actually have a camera (you can attach a gopro with zenmuse gimbal but not worth it if you don't have a gopro already and you would have to buy a gimbal for it)
I wouldn't go for a Phantom 1 if you're not on a budget
If you want some cheaper drones go with 3DR Solo (requires a gopro) or Yuunec Typhon Q550 (a bit pricier than 3DR but it includes a camera)

Thanks for all tips! I will consider what you guys suggest. And I can see that Phantom 1 is not a piece of advice for me to use.