Trade planning, for someone else, is a Hard question. But since the Game goal is max profit over 3 months, it gets easier. I wouldn't personally worry about diversification. As for using margin trading, IMO stay away, in a game or real life.
I post it's all in the numbers, often, at the board. And one needs to set up a business plan to attain success, trading the market. If your business plan is get as much gain as possible, in a quarter. That plan should be designed differently then one producing income or retirement funds.
Thus you want to trade in the small cap area. Because math produces larger gains, the less expensive the stock. Also you receive larger gain, when a stock price increases, then when it decreases. So shorting should be an exception, more then the rule.
Swing trading in the under $15 range, would be the sweet spot for a 3 month trade plan, with largest profit as goal. If the goal was successful trade ratio, price range wouldn't matter as much. You could diversify and use position sizing to reach a fixed financial goal. Building some safety into your wants and needs business plan.
Margin trading, IMO is mainly for high risk gamblers in the market. And trading a margin account, requires much more attention being payed to both your account balances, (especially if pattern day trading). And plays that are active. Gain/loss level, will effect overall profit/loss on margin traded round trip trades, as gain/loss interest; on loan proportion, will effect results greatly. (They don't take the loss, you do.) Add to that; there are so many rules, over seeing margin trading. Event with attention, you may end up with unexpected charges and fees, when the trade is complete.
But hey, if a stock is going crazy and you want to go large, can't beat an extra $100k in the mix. Just remember to take profits when they present. As personal losses increase larger on a margin trade, when a retrace doesn't bounce. (page 2 in the link above) Really really need to protect those gains, when using margin loans. Plus break even is now margin interest, fees and regulatory costs, higher then entry.
News 
Market Data 
Discover 
