The best procedure is to do a fresh install on the SSD. In fact, all your other drives should be disconnected while you do this, to ensure that it's not using the boot loader on your old drive.
If you don't have the patience / time / compulsiveness to re-install, you will need an SSD at least as big as your current OS partition's data. You can do a backup with something like EASEUS To-Do backup, and then "Restore to dissimilar hardware." Just copying the partition, or files, or doing a clone will leave you in either an unusable state or a bad state.
With that price range, you are probably limited to a 64 GB device. Maybe http://www.newegg.com/Product/Product.aspx?Item=N82E16820148441