I think, there are two ways from earn Ethereum.
1.Buy some Ethereum and start trade with altcoin and make more Ethereum.
2.Work with Bounty and signature campaign Who give direct Ethereum coin and Earn Ethereum.
The first one is the best option to earn Ethereum and use coins for trading or wait some time that value will rise.
The second one is to find an ICO that their token is based on ERC20 that can be applied and integrated into Ethereum wallet.
Additional, offer some services if you're a developer for example, instead of you'll be paid with cash - you can demand as cryptocurrency or Ethereum coins instead.
Last but not the least, Ethereum mining. This way of earning will require pre investment but not on buying ethereum coins but for good and epensive hardware that can mine more within a period of time.