Just to add a bit more info to the last three replies.

Speed: what the cards says and what you may get are going to be totally different things.
eg. a 300Mb/s card won't get 300Mb/s in the camera. Just the way it is.
Then you can have two cards that both do 300Mb/s, and the camera may transfer at 100Mb/s(to the card) but not every card will do this 100Mb/s either. Some more, some a bit less.
So base you choice on value for money .. why I recommended the Lexar + card reader link.

Another car brand worth searching for for your 90D is Adata. I have two very old, very heavily used Adata cards, my two longest serving cards and if they weren't 1 and 2 Gb in size, still be in use. Adata have a nice UHS-II card that tested well too.

What Am said: USB3 connection from card reader to PC is very handy. Not all USB3 computer ports are made equal. Some only barely faster than some USB2 ports. If you have any issues down the road with this, just post about it.
Otherwise you should get a minimum of 100MB/s from card to a high quality hard drive. And again, not all hard drives were created equal too, so YMMV in that sense.
But the difference between specific hardware can be enormous on the card to computer side of things.

Of course you need to give yourself a rough budget, and as you haven't done so, and our idea of a half decent budget to work with(mine of about $100) may not work for you. No problem!
As said earlier, nothing wrong with just getting one from Officeworks for $20-30 and be done with it and just use that card(eg. Sandisk UHS-I 90Mb/s card) and just use the camera as the card reader.