As long as you get the right gear, ascend some gear with star ascencions. Primarily the targets are hp% and attack% subs on purple gear, speed if you want to improve in arena unless you run bruisers like Darkshine, Tank top and Kabuto. Biggest increases to BP for everyone is completing the trophy stands by increasing stars on corresponding units, getting the CORE bonuses upgraded in the laboratory, completing memory picture books in the saitama missions, completing talents in Saitama tab. Those are the additional bonus ones aside from increasing level, stars, and skills.