User blog comment:1756cadence/shadow craft/@comment-25159055-20140727010541

Start out on Campaign to get a hang of it. Don't spend your tutorial coins. Higher the difficulty on campaign = more potential coins. After you feel fairly secure there, go and try to last as long as you can on Survival. Keep trying. Keep doing this! Soon, you'll be able to afford more guns from the shop... buy those! Also, beat Area 52 on Campaign to get a pistol that can be used in all modes.

The default weapons you start with are awful. You're going to want something - ANYTHING - to replace them. Hope this helps!