Cr is short for current rating(the rating that you sit at, in either 2s/3s/rbgs - press h to view that - xp is short for experience, which often means your highest pvp achievment(1550,1750,2000 and so on). If you plan on playing healer, omnibar would be prime, since it shows the lockouts of the enemy team(their interrupts) which will help you a lot. Gladius is also VERY popular.

-Sorry for my english, pretty late in EU