Best Way to Migrate 100 tables To New Database
I would recommend backup and restore method.

If you are on sql server 2008R2 and up, then standard edition will allow you to compress the backup, so that you can transfer it to the new server relatively faster than using an uncompressed backup.

Once you restore the backup to the new server, just drop the tables / SPs / Views / Triggers, etc that you don't need. 

After you drop the tables, just do a one time shrink (with Some Caveats) of your database to release space back to the OS. Note for when shrinking use DBCC SHRINKFILE (not DBCC SHRINKDATABASE)

Note: It would also be a good idea to "truncate" the tables (as @shanky pointed out) - if the tables are not having any FK relationship to other tables.