With $10M approximately, if it was ME... I would invest in movies opening within the next 30 days or so... these movies offer the best chance of going up in price (if you long them) or down in price (if you short them). Opening movies is one of the fastest ways to build your port... it's NOT the ONLY way... but probably the fastest way other than daytrading - which is tricky and more risky, in addition to time consuming.
I would play the openers, and try to pick ones you think will do well (or poorly) and max out if you are willing to take a shot. Sure, it's a bit risky, but it's ONLY play money, and if you're looking for something with little or no risk, then choose starbonds - as you can predict what their adjusts will be.
Quite honestly - for me? Openers are still one of the most fun aspects of the game, and yes... now that my port is huge, I can afford to lose all I invest in one... but again...openers offer the fastest way to build your port.
Other than that... look for playing IPO's for short term gains.. they too can offer some good movement. Perhaps invest in a fund or two that you are interested in and see how those fund managers buy or sell various stocks they hold... a good way to learn as well.
Buying the options of opening movies is also another way to make some good gains in a short amount of time. You must think "short term" with a smaller port you are trying to build. Don't invest in any movie (in my opinion) that is further out than 30 days... it ties up your $$, and makes you wait a long time to earn much... you can make more $$ by investing shorter term in other stocks, bonds, options, etc...
Good luck.