How long does it take to build credit rating?

Iam just wondering how long does it take to build a good credit rating to get a mortgage?

right now iam saving up and have around 15,000.

i have never used a credit card before until recently and i plan to use my credit card to purchase everything starting from now on. On average i believe i would spend £500 a month using my credit card.
Added (1). i will be paying everything in full on time.
Added (2). if age matters iam 24.

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