Do what the prior poster said, however, if you cannot push for PEN without comfortably doing so. Don't. I'd suggest focus more on raising your knowledge in general. This means doing a lot of hard grinding. This will probably be a little boring, but the payoff will be worth it. Do Elion knowledge first, get all of the books you've missed, monsters you've missed. Get the locations on the bubbles in the map to 100%. Those will raise your overall base cp, including your alts. Once you get to a point where you think you've done as much as you can and you've hit a progression wall. I.E, desert collections. You can switch gears and start working on boss rushes, hadum knowledge and working on your collection log. Getting your collection log should be a priority as well while grinding because every little bit of cp adds up quickly.
Boss Rushes, Ancient ruins, and finding a good active guild that does Guild rushes as well will definitely help bump your cp overall to the higher tiers. It's a steep hill to climb from here on and it's a long and hard work. Good luck in your journey.
Also, if you have the resources, go ahead and check your crystals, enchantments. Get rid of anything that's crit damage, etc on your gear. Those cap out quickly, if you can slot in atk and def, do so. Every little bit helps. You can check what can be enchanted on your gear prior to it by clicking auto enchant or clicking on the top left in the enchant menu.