Will not be able to upgrade ships or get skins without crystals and gems. The drop rate for them is so slow, you have no choice but to spend real money. Ships are completely useless at higher levels without these upgrades, so you essentially hit a pay wall. The walk throughs are meaningless, because the person doing them has a fully upgraded ship every time. I cannot progress past where I am now I've been trying for days, I am uninstalling this game and I'm not even going to miss it.