This just might be The Red Queen by Victoria Aveyard.
Mare Barrow's world is divided by blood—those with red and those with silver. Mare and her family are lowly Reds, destined to serve the Silver Elite whose supernatural abilities make them nearly gods. Mare steals what she can to help her family survive, but when her best friend is conscripted into the army, she gambles everything to win his freedom. A twist of fate leads her to the royal palace itself where, in front of the king and all his nobles, she discovers a superhuman ability she didn't know she had.
She meets the silver crown prince Cal without knowing his identity or disclosing her own. She falls into the pit where the Queenstrial is held. She displays electrokinetic powers even though being a lowly red.
Finally, many reds are conscripted to fight in the endless a war with the northern Kingdom of Lakeland and either return maimed or not at all.