To make an open position, it is better if we divide our equity to hold 1000 pips. If we have $1000, we can open trade using 1 lot and if we have $100 we can make open position using 0.1 lot. For a note if we use this kind of calculation, do not do martingale that can make you risk higher. Do cut loss or add stop loss in all your open position to keep you have safer trading experience.