Bitcoin investment is not that hard to determine, you could choose any investment which accepted bitcoin as a method payment. For now , it's HYIP , PTC or gambling . Investing in a bankroll of online casino isn't a bad ideal too.
I would rather leave my funds in an online casino bankroll that is very trustworthy and has been in existence for a very long time than ever try out HYIP. HYIP sites are more like you gambling with your funds, you may be lucky to get in very early and then you may not be lucky even when you get in early cause they might be looking for first starters.
PTC is more like faucets to me and you cannot even earn much and the best is to have some good skills to earn and increase your funds gradually cause it is hard to find legitimate investment site these days.