The OTC Markets Group (POTCQX, OTCQB, OTC Pink): Formerly known as The Pink Sheets, these markets are considered very risky for penny stock investors. Since they have such a low standard to get started, and almost non-existent fees, just about any company can be publicly traded on them. By avoiding penny stocks trading on these markets, you can reduce the vast majority of downside risks of investing in low-priced shares.
ECN/Level 2 quotes: ECNs, or electronic communication networks, are computer-based systems that display the best available bid and ask quotes from multiple market participants and then automatically match and execute orders. Level 2 is a subscription-based service that provides real-time access to the Nasdaq order book composed of price quotes from market makers registering every Nasdaq-listed and OTC Bulletin Board security. Together, they can give you a sense of orders being executed in real time.
In terms of diversification, the greatest amount of difficulty in doing this will come from investments in stocks. As mentioned earlier, the costs of investing in a large number of stocks could be detrimental to the portfolio. With a $1,000 deposit, it is nearly impossible to have a well-diversified portfolio, so be aware that you may need to invest in one or two companies (at the most) to begin with. This will increase your risk.