From what I can glean of your posts, you are likely going to find (whatever) cards you're looking for in the arena.
Start with Bronze (It's a little more difficult than AI3), and just keep at it. You'll soon get some weapon rares, and maybe some shards from the special spin, if you can win 5 games in a row.
After you either get bored, or want to try something more challenging, try your hand at Silver arena (this one is a little harder then AI4).
Once you can comfortably farm Silver, then you might try your luck in PvP-1.
After that, build a deck exclusively for False God (AI5) grinding. These will net upped cards, on successful spins.
For Gold, and later Platinum arenas, you will need some specific deck types, in order to grind with some rate of success.