For the sake of helping a new player,

almost all the response above aren't accurate enough IMO.

at lvl 75 is a critical time where you upgrade your equipment. Complete the ninja exams and get all to orange +1 if you are able to pull this, you will be getting a fair advantage over other players.

2. Get your summon runes to lvl 5, 6 is better put it up everything at 1 slot summon and use ur orange summon in that slot, summon runes gives you alot of BP boost.

3. With the BP Boost get it TI32k Itachi brothers normal, once you do you will be able to get to 36-38k in no time if all ninja tools are orange.

4. Reforge ninja tools with crit stats, att stats and nin stats in all your orange tools, ensure crit stats to be above 60 this stats generally give alot of BP as well.

5. ALWAYS refine before you do purify, PURIFY is the last option that you want to bet your CP on due to the wide range of RNG and possibilities.

6. Upgrade your Ninja Tactics, lvl 3 - lvl 4 at your level should be good. this Reaps the highest benefit with the lowest amount of CP.