So, if I use this relay with 168R, plus other one (eg:12V to have more Ampers to pass through >300W) I will have problems and blow up Arduino?
I'm not certain... but I think you are misundertanding how relays work still.
You want to use a transistor to drive the relay for 1 simple reason. When you are even slightly close to maximum limits, you need a way to "buffer" the load away from the device with a limitation. Meaning: Protect your arduino PINS.
If you don't mind replacing the $5.00 CPU instead of $0.95 Transistor then I guess it's OK to not use a transistor.
NOTE: BUFFER --> Something that lessens or absorbs the shock of an impact. A relay coil is either energized or not energized... (this is what closes the contacts) and with a relay the most impact occurs during a transition from off-to-on as well as from on-to-off. These impacts (spikes) can affect or even harm the Arduino pin if tolerances are exceeded.
The relay contacts isolate the MAINS from the control circuitry. However, as you might notice... any low current, low voltage relay that can likley be driven "directly" by an Arduino Pin, may not have the magnetic "power" required to "close" high voltage, high current relay contacts.
Also, do not confuse the relay's Current and Voltage capacity ratings for the controlled contact(s) with the relay coil's recommended voltage rating and current needs.
The 2Amps and 220Volts (300watts??? as you mentioned) markings have literally nothing to do with anything on the COIL side of the relay... They only relate to the CONTACTS side.
And if they do relate to the coil side then do not even consider this relay as an option. 
So, if you want drive a 5 Volt Relay or a 12 Volt relay, you will get advice from those of us who remain cautious about designs to say, you need a 1K resistor, a NPN 2N2222a and a Rectifier Diode like a 1N4001 to build a circuit that will drive the relay and buffer the load away from the Arduino Pin.
Sample Circuit below.
http://www.arduino.cc/playground/uploads/Learning/relays.pdf
I would like to see you not expire your arduino at a young age.