It means that you have leveled up 25 times, since the starting soul level for Royalties is Soul Level 1.
Things happen a bit differently if you're in physical form or soul form. In Soul form you'll get boosts to your attack power the closer you are to Pure White World Tendency and Pure White Character Tendency, to a maximum of 20% boost if you achieve both at the same time. The contrary effect, in Pure Black World and Character Tendency, will decrease your total health to a mininum of 40% of your physical form health.
It's better to play the game in Soul Form if you're trying to affect the World's Tendencies, since each time you die as Physical form, the World Tendency shifts to black, and each time you kill a boss, the respective World's Tendency shifts to White, so you can neutralize both effects if you aren't careful.
Take your time with the game, there is tons of things to learn, timings, dodges, counters, how a shield works better than others for what situation, you'll gain that experience with time.
Helping others doesn't really spoil your game, since even if you defeat a boss that you haven't defeated yet as a Blue Phantom helper, you'll still have to defeat the same boss by yourself in your game.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"