i have already use paypal, But i want to know which payment gatway is best like paypal , it must be a free
the best is the one that gives you the lowest commission rates for your level of sales. they are all slightly different and you'll probably have to make a spreadsheet and calculate it. you might also want to look at their reputation and count that in your decision.
You asked a very open-ended question, so the best you will get are general replies (like mine).... First, there are no free payment processors. Any company that tells you they are should not be trusted. Second, you did not define what you meant by "best like paypal". Besides PayPal, my company also uses Payza and Skrill (formerly AlertPay and Moneybookers respectively). Payza has an OK API, but basically zero customer support. Skrill is a total pain to get setup (not technically, account-level setup), but they have a bit more customer service and a platform I trust a little more.
Paypal is one of the most preferred payment processor worldwide, though there have been many instances of frozen accounts. If your customers are Indians, this could be a solution: https://forums.digitalpoint.com/threads/indian-payment-processor-similar-to-paypal.2660684/
there are many payment gateways like plimus/regnow/moneybookers/avangate and best from all is paypal.