Money is a major factor on how the player has a high power. This is why that player will be considered as a whale. At this point, don't brother trying to compete with that person and worry about the other f2ps that can beat you (I can't believe I have to say this because this should be obvious).

Also, the player may have decided to stop leveling by limiting how much exp he gets and getting as much power before they decide to level. This is something you can do as well. One of the first thing you need to do is stop doing the main quest as it gives too much exp. Learn what needs to be updated for your character before you decide to level up. Only continue with the main quest only to update your equipment or need new awaken material but do this after you max your equipment/awaken ninjas. Also consider about saving your coupons and deciding when to spend. * with ninja treasures until you have a good amount of power before you save for an event ninja.

Those are some things you can do to avoid being food for all players, which will ruin your game experience. I'm not going to list out everything that can help you as it is a long list and you should see advice about the topic if you use the search bar. If you make the necessary steps, you won't be at the bottom between the players you eventually meet.