I start with demo 10 000, but after 2 months have 2800, so I not sure that this good minimum capital for start
Well, that depends at what level you are trading. If you are a beginner, you must not risk a big amount that you may regret losing. Instead, start small and find a broker that has low initial deposit requirements. Once you have gained some experience, you can choose an amount as per your pocket.
Minimum Capital for Day Trading Forex
For a little more versatility, 500$ can give lightly more returns or income. However, 5,000$ might be best because it can help you create a fair amount of income that will compensate you for the time you’re paying on trading.
Most Forex brokers have a very low minimum requirement when it comes to opening a Forex trading account. On average, you can trade with just 100 USD in starting capital. In some cases, Forex brokers also allow you to open a micro or a cent account which allows you trade with just 1 USD.
Work on a strategy first and a solid trading plan. When you have proven to yourself you can trade consistently, on a demo for example, you can do the FTMO challenge and get funded. The minimum capital you can get with them is 10k.
I am not promoting anything here. Just an option for people who do not have a lot of money.
You can begin trading with $10. However, this will not make you more profits. Since in forex trading it is inevitable to lose money, you will require a decent capital to begin and learn from. I think an ideal capital is anything between $1000-$1200.
I feel like this account size is just asking to be blown. 
No minimum, the most important thing is to know how to pick your trades. Some brokers even accept account opening of 1usd. Once you know how to trade you would know the right amount you need to trade with
The best minimum starting capital to start with IMO, is one that if you lost, there would be some pain associated with if you lost, but not enough that you need to put food on the table. The focus to begin with should be on consistency and not a lottery winning. One thing I do is add a little bit to it each week. Treat it like your 401k. If your consistent and adding a little bit each week or month, you can grow a small account fairly quickly. Just don’t try to rush it.