I tried out Eternal and found it to be rather nice. There's no obvious reason to pay $20 up front for Artifact when you can play a solid game in Eternal for free, unless you're looking to hawk cards on the Steam marketplace (then Artifact may be up your alley).
Getting cards, event tickets, and campaigns is stupid easy as well. Just keep hammering Gauntlets to get freebies. Typically you get three loot chests with gold + a card or maybe even a free pack. Hell in one chest I got a ticket for a starter draft gauntlet against AI opponents. Got to keep the entire deck, plus got more rewards from winning the . . . whatever they call it. It was like a gauntlet, but I had to draft cards to add to a starter deck and play that. Wound up with a Time + Nature deck that worked pretty well.
The five starter decks you get are functional. With a little tweaking, the starting Justice deck can be pretty powerful.
Multiplayer seems okay. I would like to see more game modes. M:tG has things like Emporer and Two-Headed Giant which can be fun. There are also some old dead styles that are not currently supported by MTGO (that I know of) like 5-colored star which are fun, if a bit chaotic.
Some of the game's critics claim that mana balance is a problem. You either get too few sigil cards or too many. Which I guess is one of the problems with Eternal being based so heavily on an M:tG like formula. Since Eternal insists on using the kind of system they do, it pays to balance casting costs against the amount of sigils you have in your deck and against the tools you use to help you get more mana. Or power or whatever you want to call it. I do really like how they've fixed the land balance problem from M:tG with the influence system; instead of having to have exact colors of mana, you instead have influence requirements on each card, so that as long as you have that total amount of influence and the right amount of mana to play the card, you can play it. If you play 3 Justice and 7 Shadow sigils, you can play any number of Justice cards so long as none of them require more than 3 Justice influence and so long as the total cost for all of them does not exceed 10.
Anyway to summarize, all it really takes is: don't use so many expensive cards, and use a lot of cards that either let you draw more cards or let you pull sigils directly out of your deck (each color has at least one common card that lets you do that, and then there's a colorless card that lets you do it in any deck; these are "deck holes" that effectively give you a 67-card deck instead of the 75-card minimum).
Once I get a larger collection and get more used to the sets in the game, I will go back to a 33% mana strategy for more aggressive deck design. Which would be 25 sigils out of 75. For now I use the recommended 30.