British English has many phrases for trust that is earned slowly.
It’s not what you know, it’s who you know: Connections matter more than skills.
To get a foot in the door: To get a first, small chance with a new customer or employer.
A known quantity: Someone whose reliability has been proved.
To prove oneself: To show over time that one can be trusted.
To earn one’s stripes: To gain respect through experience.
Early days: It is too soon to judge.