Hi there! I'm not sure there is really a helicopter that anyone can say is the "best" to start with. You'll get many opinions, for sure. However, some good collective pitch helicopters to start with would be a 450 or 500 class helicopter. I've never flown a Dynam but I've seen videos of them being flown very well.
For your very first heli, a 450 is definitely not the one to go for.
You want a small coaxial or fixed pitch heli like a Blade CX2, MSRX or similar.
There are many brands out there, Blade being one of the most recognised.
Then the best investment is a simulator like Phoenix, Real Flight or AccuRC.
This will teach you a tonne, and doesn't cost a thing, when you crash
If you are impatient to start flying, get a fixed pitch helicopter around the $100 - 150 mark.
But if you can restrain yourself, invest in a proper simulator and a transmitter - then, get a helicopter.
I echo what Lee and stokke have mentioned. Get something like a blade 120sr or the msrx. Once you get a few months if flying under your belt then look at a 450 or a 500.
You should feel comfortable in all orientations before making the jump. For the 450 size kits I can recommend either the align 450 dfc or dominator. The other kit I recommend is the Gaui X3. I have the Gaui and it flies great and takes a decent crash quite well. I put mine in nose first without a canopy on and the frames and battery survived impact on cement.
Start small then work to a bigger size. Some people will skip the 450 and go straight to 500 or 550 size. They are much more stable over a 450 while in hover and in flight. Costs go up at this size so make sure you feel comfortable with flying before the jump.
The Dynam 450 with it's stock TX is a real nightmare to set up properly for a beginner.
I found a tutorial on setup somewhere, I will post a link when I find it.
You may be better to invest in a decent transmitter and receiver.
I echo what everyone else has said, a flight sim and a cheap, stable mini/micro.
I would suggest the V911 from Banggood.
It is cheap, stable, quite robust and will teach you all the basic orientation skills.
And you can fly it inside.