Update: Game has been removed from App Stores. Check out this post for more information.
Note: As of now, players in forums are reporting that there seems to be discrepancies in each accounts' energy recharge timings, energy cost for Arena as well as differences in crates' gem costs.
First and foremost, this is not a card game but more of an RPG game using cards as the characters. I played for a while and initially thought that it was IAP-heavy because I got stuck at around the third stage. However, I choose to stick with it and played some more and I soon figured out that you actually need to grind a bit at the training missions to level up your cards. The game was just designed to have a steep difficulty curve right at the start. Update: I seem to lose even the replayed stages which I have completed before so the difficulty is kind of erratic!
It turns out that the game is surprisingly good. It has nice graphics and card art along with the Star Wars music and sound effects. (It even uses parallax effects; I tilt my iPhone 5 and the stage looked 3D. Unnecessary but cool nevertheless.) The UI is nicely designed but I felt the tutorial left out information that you can feed cards to level up your other cards. The gameplay consist mainly of taps but I encountered lags during battles as I tap to attack but had to wait. The game has an Arena mode (Boneyard/Coliseum) for PVP and I think the opponents are AI controlled. In all, the game is very polished and enjoyable without spending cash. Quite a lot of cards can eventually be levelled all the way to the highest tiers and there are many chances to earn cards in the game.
Update: I notice quite a bit of humour in the game (normally pop-ups) which is a nice touch. For example, I tapped too many times while attacking causes a Darth Vader pop-up warning. I also find the game more enjoyable on a tablet screen than on the iPhone. There is also no rush to complete any "events" in the game so the only limit is the energy timer which is great if you do not want to spend a lot of time on a game. Edit: There are daily special missions which seems to be the only way to get high tier promotion items.
I think the main "cash grab features" of the game is the spending of gems to continue a failed quest and to increase item/hero slots, both "borrowed" from Puzzle and Dragons. I just play ignoring continues and managing my slots well to avoid them while progressing the story.
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I was coming up with tips as I played but I found a site, writepart.com, which covers most of what I want to say: