optimization for create index on large table

I have one doubt in sql server . Table : emp

 col1  |   Col2   | COl3  | col4 | col5 | col6| col7| col8|col9| col10

in the above table have data approach 3 crore records.all columns datatype is varchar only. for retrieve select query optimization purpose I create cluster index on emp table. create cluster index cl_emp on emp( col1 desc,col2 desc ,col3 desc,col8 desc,col10 desc)

In this process to run above query its taking more than 1 hour. here create indexs and select query both take more time I want reduce time and even when I try

select col1,col2,col3,col8,col10 from emp

that time also its taking more than 50 minutes. please tell what steps I need to processed to give good performance for large tables in sql server .