Any good quality card should work fine. I’d suggest SanDisk (my personal favorite, never failed me yet) or Samsung. And the higher class cards will be faster. Depending on how you plan on using it, that may or may not be important to you.
As to size limit, I think it’s the size of the filesystem that you format the card with. For OSMC (linux) that would equate to no limit on card size, as no SD card has that much capacity
EDIT: I should also point out that the OSMC SD card has a lifetime warranty.