Back in 2014 I used to own a mining rig (6 R9 270x's). I primarily mined DogeCoin, shut down the rig when I moved out for college because it was becoming a little too unprofitable with the competition and I couldn't really maintain it/bring it with me.
I also am a huge fan of NEO, love their Smart Economy and own some of their coins to generate GAS.
I can vouch for these two methods. The mining rig back in the day paid for itself and made a little extra before I shut it down, making it a profitable hobby that helped me dive into cryptocurrencies. Mining is an important part of maintaining security in proof-of-work coins, however it does waste a ton of electricity, so make sure to look into how much your electricity bill costs before you commit too hard.
An important thing to note as well is certain coins are more/less efficient to mine in certain ways. If you tried to mine Bitcoin with your graphics card, it is terribly inefficient because you're competing against ASIC's, which are specialized hardware built to be REALLY efficient at doing one thing, and that's mining. So if you are going to mine with your graphics cards, make sure you're doing it for a ASIC resistant coin. I could be wrong, but VTC/XMR/ETH/FTC and a few others are ASIC resistant, so you're in a fair competition against other graphics-card miners when you mine those coins.
RE: What are the ways to Earn in Crypto Space other than Investing in it ?