There really is no "recommended " file size.
File size is relative to your needs and what you need to put in the workbook and the bigger the file the larger the PC's memory and processing power must be.
A 10mb file might be fine on some PC's but will struggle on others.
Also depends on what's in the file 1,000's of lines of raw data will be a smaller file than a couple of hundred lines of heavily formatted data, for instance