The answer to your question depends on factors such as:
1. The Minimum Deposit at Your Broker
2. The Price of the Instrument You Want to Trade
4. Lot size you want to trade
3. The Leverage you are using
The minimum deposit will determine the smallest amount of money you can put in your account or wallet and so it is a determining factor.
Different instruments have different prices so if you want to trade a forex pair like the EUR/USD you're gonna need less money than if you want to trade something like Bitcoin or stocks.
The lot size or volume or quantity also determines how much you will need to place a trade. 1 standard lot costs a lot more money than if you want to trade say 0.01 lot.
The leverage of your trading account is also important because it determines how much collateral (margin) you will have to deposit with the broker to kickstart the trade.
Brokers will usually allow higher leverage for popular instruments like EUR/USD & lower leverage for less traded/high risk instruments like Bitcoin and stock CFDs.
So with the broker I use, I have up to 1:3000 leverage; if I want to trade the smallest lot size (0.01 lot) of the cheapest instrument (EUR/USD) then it usually costs me around $2 to open the trade and still maintain some free margin above 100%.
The $2 it costs me to open a trade is because I am using very high leverage (which is risky). If you are using a lesser leverage than 1:3000 it is going to cost you more to open the same trade I did, because your margin requirement will be higher.
