There are some bad things about this game, but it's because I have played this game for like a year and have seen some unfavorable changes. But if you have just started up now, you wouldn't be able to tell the difference. But one bad constant thing is that people who spend actual cash on this game can get good fast and by good I mean good gear, after that it all depends on player skill.
Yes it is possible to trade in game coins for gold (cash) and use that gold (cash) to buy boutique items (in game cash shop).
Honestly I am a bit biased on which server is the best hehe because I play on Lost City (PVP Server). So in my opinion Lost City is the best server xD.
PVP servers are able to pk ANYONE at ANYTIME past lvl 30 and when out of a Safe Zone. PVM servers however can put on a mode where they cannot be pked whatsoever. Now this is not to say there is no pk, because there is also a mode in PVM servers that allow open pk, but this mode however, once activated, requires that you stay in "pk mode" for atleast I think 7 days.
All in all it is a good game, and if you wanna get a good head start you could spend some fg for some in game coin.