Inscription will always be related to your identity, occupation, hobbies, mentality and many other situations. Others don't know your situation, so it's hard to say it properly. It's best to write your own words. You write the inscription for others, and I'll write it. Of course, it is ok for others to give you a reference.
But some common ones are more general, such as: rewarding diligence by heaven, respecting morality and carrying things, and so on. Or write some poems and proverbs. For example, learning the sea is endless. Burning passion depends on self-improvement and so on.
This is not fixed, according to your own situation!