The in-game currency is gems (wow, how original) which you will absolutely require in order to progress. The unfortunate thing is that its impossible to gather enough gems by simply playing the game. Ive been playing this off and on for the past 2 weeks and in that time, Ive been able to earn 204 gems. The very first upgrade slot for the very first weapon, the dual pistols, costs 140 gems. Id hate to know how many gems would be required for the other 6 weapons, not to mention the many outfits and their requisite upgrades.
Its very unfortunate because the game can be entertaining (for a "runner") but as a gamer, I enjoy the challenge of playing games to win, not paying. Guess Im not the target audience for this title.
Caddoc about Lara Croft: Relic Run, v1.6.77