Are you asking for the initial size or for the total size over time?
If initial size, just set it to 10 MBs and set it to auto grow 10%.
For total size over time:
That isn't an easy question to answer, as varchars are variable (can be any size), so it all depends on the amount of data you are using and how many rows you plan to hld onto.
But lets assume you are using all of the characters in each column:
25 columns * 100 characters * 2 bytes per unicode character = 5000 bytes per row
DB size is roughly = X (number of tables) x Y number of rows + Z (size of structure of tables)