hi,man,You need a certain amount of Ethereum as a fee to transfer, so if you don't have Ethereum in your wallet, you will not be able to complete the transaction
This is the reason people need ETH ? to invest ICOs in Ethereum platform?
Not only to invest in ICO, ETH (very small quantity) is needed to be included in fees when you want to transfer coins you have received after investing in those ETH based tokens.
without ethreum cant i proceed any tansaction? if no , then how can i sell my ethereum tokens to get ethereum so that i can process transaction
No you can't so even if you have received those tokens for free you will still need to spend some ETH in fees to be able to sell them or move them.