Hello and welcome here!
There's a lot to say about these questions, better have a look on this section: https://oldsquad.ro/forum/forum/159-info-rules/
1. The currency is based on jwls and or Credits (which you can get from donations or from other players via market)
2. BK/RF/Summ looks like the strongest in PVP in this stage of the game.
3. Elf is not good, at least not PVP, is decent in PVM but not great.
