Without knowing your financial status, risk level and amount of knowledge you have when it comes to trading, you should always step in to a trade instead of going all in as a rule. Also it seems like you do not have a trading plan, before doing any type of trading, I would suggest for you to stop trading, and create a trading plan. The most important part of the trading plan is money management. Here is a link with a short description of money management: http://financialsaint.com/cms/cms/viewer/page/422
Not enough information to base a decision. Some systems do better pyramiding, many fare batter with an all-in / all-out approach. You need to either backtest both with simulated trades, or if you have enough of a sample size, analyze your real results and come up with the answer yourself. Adrian