It took me quite ahwile to get to $1B....but when *I* started playing, we could not short stocks, there were no derivatives, and very few Funds...so the time it took to get to $1B was longer than playing today. If you have been here for 2-3 years with only $16M, you either are not playing as often, or are not taking advantage of all the things you can do to earn $. I'm not saying that to be critical, but just pointing out there are lots of ways to build your port now.
As PRodQuanta pointed out, playing openers is probably the FASTEST way to build your port with the exception of day trading - which is tricky if you are not here a lot. When you play openers, always try to max out. Nothing more frustrating than playing an opener, and finding out it adjusted 10+ points, and you realize you only owned 20,000 shares... you make $200,000 instead of $1M. When I started, we could only buy 10,000 shares..so you can see how it can really help you build a port.
Try to play the games HSX gives you for 'free' money. It's at the top of this page where it says "Need H$." If you win these, it may add $10,000, $50,000 to your port, and every little bit helps.
I think with $16M port...I would say do NOT hold many stocks that are further out than 2-3 months. It ties up your cash, and you don't have $ to invest in IPO's that may rise (or fall) quickly in a few days. Plus, you may not have the cash to play those openers I talked about.
Starbonds, as was mentioned is quaranteed money since you know when they adjust and usually by how much.
I have been playing since 1998, but I don't trade a lot any more...buy some stocks here and there, I always try to play openers (still the most fun part of the game I think - trying to guess how they'll do) and other funds, etc.... but I am coming up on $2B... I used to think I'd retire when I hit $1B, but there are so many people ahead of me now, $1B is not that big of a goal any more.
And...just to make the REST of us FEEL bad... you can keep an eye on Grory.. who is #1 on the rankings... she started a NEW port at $2M, and built it to OVER $1B in a year...just to show the rest of us that it COULD be done...but she's a daytrading wizard.
Good luck!