the strategy that best works for me is to poke my head out and shoot at the sniper until he dies and drops 100 gems or so. So this about 8-10 times and you'll have enough for the cryo gun. Sorry the game takes a bit of farming early on, but I believe that it gets a lot more fun from there. Definitely check it out again if you have the chance, I'm pretty sure someone will post a video... If not I'll upload one myself this weekend 😊