Founding Partner @ Quexor Group. Have worked with many start up companies to help them define their product strategy and execute on go to market strategies. Translate technology into market need and help companies monetize on the market need.
Firstly - it is not always about spending a fortune on marketing and advertising. It is more about laws of physics than math. If you can put enough force into things that all increase the energy of that force - meaning, doing less isolated efforts of marketing but more integrated approach.
Look at your target audience, where do they usually go for advice on international investments - Google ad-words is a good start but again, that is where active seekers would be found and you should have planned and implemented a good SEO approach. For passive prospects (not looking actively for international investments)- you would still need to generate interest through branding campaigns. This is again where, if you plan it well, perform research on the right channels for adverting to your prospects, some are free online, some are worth the spend. Also, look at your partners, and co-marketing campaigns in this time are a real asset as well.
In a nut shell, there is not a cookie cutter solution and not one size fits all. If you spend more time planning, you will spend less money and less time will be wasted on execution of your marketing and advertising campaigns.
I would be happy to have a call if you want to discuss this in further details and share some of our experience with such campaigns.