A trade can be directionally right and still cost more than you expected to enter and exit.
Fees are charges for using the platform or executing an order. The spread is the gap between available buy and sell prices. Slippage is the difference between the price you expected and the price you actually received.
These costs matter more when you trade frequently, use large size, enter thin markets, or hold positions through funding payments. A published commission is only one part of the cost.
Before using a market, check the fee schedule, typical spread, funding behavior, and how the prop firm calculates equity. Practice in the same market conditions you expect to trade.