SQL 2012 :: Parameterized Sort On Multiple Keys Possible?

I have sp that works with GUI and have an opton for sort field/ collation. But I noteiced that if I do level on very generic key like <Level> in my case it does the job, but output does'nt look right after that all names, account numbers are messed, so I'd like to add second sort column and looks like it can'be be done with my syntax, I tried to play adding second column and failed.

Select * from T1 order by Level, FirstName

Looks like it only can be done with Dynamic...

DECLARE @SortColmn VARCHAR(10) = 'Level'
SELECT *
FROM TABLE
CASE WHEN @SortColmn = 'FirstName' AND @SortDir = 0 THEN FirstName END DESC
,CASE WHEN @SortColmn = 'LastName' AND @SortDir = 0 THEN LastName END DESC
,CASE WHEN @SortColmn = 'Region ' AND @SortDir = 0 THEN Region END DESC
,CASE WHEN @SortColmn = 'Level' AND @SortDir = 0 THEN [Level] END desc --<@>>< THEN FIrstName asc ???