Stopong Point for derieri

My derieri is currently p6 i just lost my 50/50 early to jericho should i grind for p7 or use my guaranteed for ban both are my absolute favorites and i am a low spender i have all side quests open in the game and i currently can only beat tsj up to sector 7 sector 8 is well hendricksons damage is over tuned(my opinion) so should i go for p7 or not(i dont have meli started when merlin came out)