Welcome Ackril! As a relatively new player I can understand some of your problems. Don't get discouraged and, like others said, check Infinite Network and other useful user-made guides that may help you.
When you play Pauper, in first few games, you have no chances to win.That's not true. Trust me, every time I play Pauper for a while, I manage to win ~50% of my matches (unless I'm very unlucky with matchmaking), and my card pool is not big at all. You can still outsmart people who run stronger decks, if they play with poor strategy.
Cards i never saw, never had, much better combos(than basics cards i've got from campaign) = loose ...First of all, you should become familiar with core-mechanics of factions, combos, synergies, etc. I'm not a veteran but I suggest you to stick with Pauper mode for a while, even if you'll have to wait longer, in order to know a good amount of main cards. Stay away from Rift Runs for now, and spend your IP on Boosters (personally, I'm sticking with Collection Boosters, purchasing one everytime I save up to 5k IP).