Do you have a merchant account? If not, you'll need to either open one at a local bank or be restricted to payment gateways that allow direct deposit into regular banking/checking accounts. There are also online merchant account providers that also offer an online payment processing gateway.
What you choose should depend on the payment sizes/quantities and the rates offerred by different vendors. Some vendors/plans charge a monthly fee + a percentage of each transaction, others charge a flat rate on a per-transaction basis. If you have few transactions, and they're very large transfers, then obviously a flat fee is best. In your case, it's not so clear. You'll need to get a list of rates and do the math yourself.
Also, if you're using a pre-existing e-commerce app or library/framework, then the gateways/standards your software supports will also be a deciding factor.
Your local bank will most-likely have a business banking department that can offers merchant services, including merchant accounts as well as a list of online payment processing gateways that they have a relationship with. So that would be an easy way to get a list of payment gateways which work in your country.