Should I rush to sign up for Amex gold 40k bonus or wait?

After finally paying off all my debt about 6 years ago I’ve decided to start using credit cards to get air miles.
I just signed up to the free virgin card and need to spend £1k in three months, which is easy

I was under the impression Amex charged for credit cards but can see the first year is free for Amex gold

The welcome bonus is 40k if I spend 5k in 6 months.

As I’ve only just got the virgin card (yesterday) can I spend the grand on this first and come back to a similar 40k welcome bonus later on Amex?
I don’t have any understanding of what their welcome bonus is normally like or if it’s a deal I need to snap up before it expires.