I'd been typing for a while when pmsupport's reply showed up, so apologies for redundancies:
1) There are three cards sequences that heal you every turn passively if put in a leader slot. All of them start at 4* (four stars) and evolve up to 6*. The best is the holy priestess, which evolves from the holy maiden which evolves from the light maiden. Next best is the saintess of the ocean, which evolves from the ocean maiden which evolves from the water maiden, and the worst is the floral saintess, evolved from the floral maiden evolved from the earth maiden. The saintess of the ocean is only a tiny amount worse than the holy priestess (except in that its active skill is different and generally worse), whereas the floral saintess is only about half as useful as the other two. Eventually, everyone needs a holy priestess. It is the single most imperative card for getting anywhere in this game, since nearly every optimal strategy requires her as a leader. However in the early stages, it generally doesn't matter which of these cards you have since they all heal a lot compared to your total health.
2) The cards range in rarity from 2 to 8 stars, but no card type other than the dragons can evolve more than twice. Swordfish 2* evolves to Spiked Swordfish 3* and no further. Light maiden 4* evolves to Holy maiden 5* evolves to Holy Priestess 6*. Zeus 6* evolves to Almighty Zeus 7* evolves to Zeus the Supreme God 8*. For a full list of any given card's evolutions, go to the wiki, where Midas (Howrus) has done an amazing job of getting nearly every card and its evolutions up for you to peruse:
http://dragonera.wikia.com/wiki/Dragon_Era_-_Slots_Adventure_Wiki3) Collecting high-level cards in this game is a difficult process. The primary methods of obtaining good cards are through gem recruits (In-App Purchases, though you can earn gems in-game in some ways) and the guild shop. Both involve a lot of randomness, so if you want to go anyplace, be prepared to wait and take your share of bad luck. There are, of course, other ways of getting better cards, though these are difficult. As you progress through the main levels of the game, you'll find better and better bonus cards available as collection bonuses for stages (that card on the right side that you get when you collect all the cards on the left side). All three of the 4* maidens I mentioned above are available in chapter 5 (though by the time you get there you probably won't need them, ironically). Another method of collecting better cards is through guild wars. I won't explain exactly how guild wars work (they're easy to figure out and your guildmates can help you), but joining a strong guild is a great way for a new player to quickly get good cards (I understand the urge to build your own guild, but that's extremely difficult at this point in Dragon Era's life, and you'll get a huge headstart on leveling your guild shop and finding good members by joining an already-established guild; I recommend "The Avengers"). There are other ways to get stronger cards, but I'll leave you to sort them out.
If you're new to Dragon Era and you didn't start with one of the saintesses as your free 6* card, I recommend you friend several ppl who do have them as soon as possible. You'll need them. Many fans of this game recommend restarting your file until you start with a holy priestess, though I personally had no trouble finding one myself. If you're the collecting type (like me) who likes to pick up one of every card, I highly recommend you restrain yourself until late in the game--you'll pick up every single card in monster lists 1 and 2 (on the wiki) by accident just by playing through, and most of the rest will come naturally as well. Don't search for them, don't evolve for them, and don't buy them from the guild shop. Just focus on the cards you need to beat the levels you're playing. In the end, much of the game will boil down to you seeking out 6* cards to evolve or skill-up to make the most powerful teams in the game, which in turn will help you reach the best prizes. For more on intermediate gameplay, check out Xanity's guide:
http://www.playmage.com/forum/viewtopic.php?f=36&t=11853I'm also happy to answer all the noobie questions you like, so post away
