2 billion gold/XP doesn’t go as far as it used to. Over 100 players will score over 2 billion points this contest on S1. Upgrading all the essences next update will cost 1.26 billion xp. By necessity, the numbers will just increase over time and affect less whalish players.
I suggest creating items that store XP and gold. For example, an XP note could be purchased for 1.1 billion XP and later cashed in for 1 billion XP. The same could be done with gold. This would make resource management easier.
Alternatively, you could use 64 bit integers.