Is this a good starter kit to buy for Arduino Uno R3?
Yes, it has mostly sensible stuff in it, and the pricing is not too bad.
The general comment is - look at the items and see just what you would want to do (play) with each. If you would want pretty much all, then go ahead and buy.
Do compare of course, the price of buying each item separately, it may or may not be cheaper - or you could end up with much larger quantities of (useful) things like resistors and LEDs for the same price..
Thanks