It really, really wouldn't A few exceptions aside, us diddy clubs (which now very much includes Rangers) spending big bucks on transfers has practically always been a total failure. Apart from the likes of Stokes, who by all accounts was bought on the implicit understandng of us flipping him in one year, all the examples coming to mind have been disastrous. Beslija, Alan O'Brian, etc. The only way to buy success so to speak, is to pay good players ridiculous wages to play in Scotland, which would cost a shit lot more than £5m.
As a bit of fun, why doesn't somebody who thinks their club could compete with Celtic by spending £5 give us fantasy football style run down of how they'd like to see it spent? And if you're a Rangers fan, don't say "well I'd expect the club to know more than me" because the club's scouting system clearly involves reading The Daily Record every day, so your shortlist is as good as anyone's.