You can choose either of them. The game is very solo-friendly and after HD release even easier. I recommend you to choose one of them if you like more lighting-fire sounds (RK) or music sounds (Minstrel). You will hear that a lot and I personaly quit playing Minstrel because I was annoyed of that instrument accords (sure.. you can switch instruments at least). Captain is somewhat slower leveling - close combat etc.
RK - great both DPS and healing, fast leveling, anti-lore class, sometimes squishy if overwhelmed - this is my personal choice
Minstrel - great both DPS and healing, lore-frinedly class, squishy if overwhelmed
Captain - very universal, always welcomed in group-play, a little slower leveling, very sturdy because of heavy armour, you can finish some 3-men instances solo, soldier pet
Elves - Dusreth (HNT104), Dusriel (RK98), Dusaran (WRD70), Dusraen (LM56), Dusador (GRD44),
Mortals - Dusgar (CPT36), ...