I have to sympathize with you new-comers. I myself joined 3 weeks ago, roughly at the time when Sundials were being nerfed. In these 3 weeks, the AI has seen massive improvement, there have been more False Gods added and even more game content (Alchemical Cards/Nymphs) being added in very near future.
I guess it is the price you pay though, Zanzarino (the game creator), devotes a lot of his time and puts hard work into coding and fixing bugs, adding new content and balancing this game for us. So, on the one hand you have a game which is evolving over time - quicker than the fact-base, wiki and forums can keep up. But the end product is a better game in my opinion.
When I started out, I reset my account 10 to 15 times to try out all the elements and see which one I preferred the most. Then finally settling for Air/Life Firefly Queen deck and grinding Level 3's, I realized there was a forum and wiki's which list lots of strategies and deck-building techniques.
The main pitfall that new players fall in, is once achieving 500 score, you get to pick a rare weapon these weapons are rare. I cannot stress this enough, make sure you read each one carefully and pick the best one for your deck. The favourite/most widely used/discussed weapons are in no particular order Pulverizer, Eternity and Lobotomizer, and then possibly Fahrenheit and Owls Eye.
The easiest way to get upgraded cards (only way?) is to grind False Gods, as you have a higher chance to win a card against these. The most efficient (most commonly used) way that I know of right now to do this is to use a Rainbow Deck, check the wiki and try them out.
Hope this helps!
And, Happy Hunting!