(4) Build a deck for speed-farming False Gods and save up ~2000 
. The point here is to play as fast as you can (forfeiting to False Gods your deck can't beat, and playing the ones your deck can beat) in hopes of winning an upgraded card from the spins. You can then either keep the card, or sell it for over 1000 .
He'd lose a ton of score doing this, which is exactly why he needs something else
Any of Tribal's other options should work. I'd personally recommend PvP1, because it scales based off score, so you'll usually get a larger boost from it than ai3.
PvP1 is
wonderful for score up until the point where you have a higher average score than most of the opponents playing in PvP1. In my experience, this point is somewhere around 1k-2k score (depending on who's playing at that particular moment). Just about every basic unupped rush will have a high win rate in PvP1.
Once you've hit the point where you're higher level than the average opponent, AI3 is a great option, but silver is actually faster I'm pretty sure (and I'm pretty sure it's by a relatively sizable amount) - monodark is a wonderful option against silver, as is antabow (or whatever grabbow you like). Please note that silver isn't better than bronze at
rares, since you're looking at a ~47% win rate with monodark (with a reasonably high EM rate) and a ~50% win rate with antabow, but you will still get some rares, and your score will go up quickly.
All in all, though, I would really recommend just not even paying attention to score. You're a lot better off focusing on gaining electrum at the early parts of the game, and score will come with it. You'll fairly quickly get away from ever needing to play the things that are a net loss of score. Arena is great fun (really, it's my favorite part of the game by a wide margin) but you're not going to make any real money out of it until you're in the higher leagues (and even then, it's less money than like a half hour of grinding). The main benefit of arena is practice at building decks using cards (i.e. the oracle card) that you wouldn't necessarily otherwise consider, and you can get this benefit regardless of the bonuses your deck has.
TL;DR: PvP1 until 1-2k score, then ai3 (for easy, steady gain) or silver (for less easy, but quicker gain). But best option IMO is to just completely ingore score and focus on money - score will come.
