you will find at level 91,94,96,97,99,100,and 102 there are better clubs than at level 90 .so upgrading now is not advisable because when you do reach those levels you will no doubt want whats best on offer....
its up to you what you can or want to spend really.
It's also a question of "how long can you wait?"
L91 is at 565,000 XPs
L96 is at 1,290,000 XPs, adding more than the original number (and time, probably)
L100 is at 2,500,000 XPs, 4.4 times the original number
The OP is at L90, 11 months in the game. Do you tell him to wait as long or even for four years? Maybe, an "intermediate" solution is acceptable?