You should get the Standard Edition—I'd recommend it at $40, so it's a steal whenever it's on sale. Note that this is completely different from the Starter Edition, which you shouldn't buy, even when it's discounted.
You should buy the Standard Edition because you'll pay much less for operators. Owners of the Standard Edition can unlock the 20 'launch' operators (the ones that Siege launched with in 2015) at lower prices. These include useful characters like Mute, Rook, Pulse, and Thermite, most of whom see tons of play.