If you want to put variables into a string, you'll have to make sure it's not part of the string itself. What you're passing to the query right now is a literal '$Variable_Test_1' which is never replaced by the value.
Instead, you can stop your literal string value.
So imagine you're trying to do SELECT * FROM $TableName;
then your expression would look like this:
'SELECT * FROM ' + $TableName + ';'