First time user

Hi, it's my first time to be issued with a credit card and I have a credit limit of £1000. Is it really a MUST that I should only spend 30% of it to keep a good credit limit? I'm used up 45% already.

In your personal experience, when you use up 50-70% of it, did it affect your credit score badly?

I'm trying to build a good credit score for a mortgage in the near future so it would be great to get some advice from people with experience in credit cards especially Capital One.