New (ish) car buying mileage...

I'm looking to purchase a Red Citigo Monte Carlo after i've passed my driving test, the question is what kind of mileage is favourable? I've spoken to people at work and they say don't go higher than 20,000 miles on a fairly new car, others say the lower the better, they're obviously more expensive though...

So do i spend £4995 for a 64 plate with 24,100 miles? 

or do i spend £6500 for a £64 plate with 13,655 miles?

or do i spend £7000 for a 64 plate with 2080 miles?

or do i spend £7299 for a 65 plate with 3692 miles?

These are just prices from currently available cars on Autotrader...

There's no real budget just means i've got longer to pay my dad back 

and the more i spend the less i have to mould the car to my liking with accessories and mods...