Would invoicing my own foreign company be better than taking a dividend?

Sometimes, but that is not a matter of preference. If you genuinely provide a service from Turkey to the company abroad, invoicing is the correct route and the transaction is a service export with its own deduction regime. The constraint is that you are a related party as a shareholder, so the price has to be at arm's length. Setting it high moves profit in a way that gets recharacterised; setting it low leaves income abroad that should have been taxed here. And underneath both, the service has to be real.