Gods Unchained is a trading card (similar in concept to MTG and Hearthstone), that is currently in Beta (and a lot of fun to play!)
The game is completely free to play. You can start now. No purchase required, though you will need an extension that lets you work with the Ethereum blockchain. The official website links to Portis, but I would suggest Metamask instead. It is super easy to install. You don't need to own any Ethereum to play, you just need an Ethereum address, which the extension will provide for you.
In-game, you will be given a number of free Core packs to open and play with, and there are also starter decks for each God. At the beginning, it will probably be easier to play with a Starter deck until you accumulate more cards. And you can do that simply by playing. You get experience for each PvP match, win or lose. Fill up your experience bar and you get another pack (5 cards) from the Core set!
In addition, each win will give you a number of raffle tickets (generally between 100-200 depending on match length). These are automatically distributed to wallets on a daily basis (though not during the weekend), as long as you have accumulated at least 1000 tickets since the last transfer.
You can hold onto the raffle tickets if you like the game and are interested in perhaps receiving a prize from the raffle (one of which is the Mythic card, Tethys). Or, you can sell them on the secondary markets at GU Cards and GU Decks (both are reputable sites with active representatives on the Discord channel). The market is very active and there are a number of players buying tickets on a regular basis.
The price has fluctuated a bit and is currently at 0.01 ETH for 1000 tickets. Not a huge amount of income, but there aren't many real games where you can earn money just by playing
Here is a link to the Official New Player Guide to help get you started. And if you have any questions, feel free to ask here or on Discord or Reddit and I'll be glad to answer what I can.
This raffle event will only last until October 24th, so get in now!